it's a waste of time, money, and just a bad idea.
novorussian forces need to be focused on ground operations, and purely rely on AA for defense. Once all is stable, and if the war really ceases, etc... Novorussia needs to focus heavily on 4 level AA defense: artillery, manpads, SPAAG, and SPSAM.
I can see aircrafts in their forces, but that should only be helicopters, for quick response deployment, evasan, and other duties. Of course, utility wing aircrafts and light cargo could be used, but no combat aircraft would be useful.
novo forces until now have succeeded against all odds, using intense guerilla warfare with elite infantry, with intel gathering and artillery dialed in accurately. One can say armour played an important role in the last 5 months.
For the AA defense of the whole territory:
with the already captured and supplied systems, I'd say they need:
artillery: at least 150 AZP S-60, 300 ZU-23, a few ZPU couldn't hurt, according to how much one can find, a healty 100 to 200 to complete the ZU-23, some KS-19 wouldn't be too much, 40 to 60 to protect the most important sites. If the need be, some vintage 85mm M-39 guns could be taken out of depots, but 85mm ammo nowadays is simply too old and not produced...
AZP S-60 is the famous and successful 57mm AA gun, puting them in batteries, with a modern radar (mounted on truck) and competent trained crews, ukraine can say bye bye to any low-slow flying aircraft, like medium military cargo planes, helicopters, attack aircratfs, and even fighter aircrafts are in great danger. This gun can be a lethal threat to any ground unit, so it can work to supress light armour, entrenchements, etc... Novorussia should seek to mount a healthy portions of them on some chassis, I think a few T-55 hulls could be used, but I don't see how novorussia could obtain T-55 hulls in quantity... Unless asking russia. I'd say T-64 hulls, but all T-64 currently on the territory of novorussia should be repaired and used as tanks.
ZU-23 needs no presentation, 23mm, probably the deadliest and most effective short range AA artillery, the more of them, the better, either the gun mount or mounted on trucks, mtlb, btrd, etc... I think novorussia already has a good number of them, but you never have enough ZU-23.
ZPU (usually ZPU-2 or 4) are KPV mounted on a AA mount, it was replaced by ZU-23 in service, but still found in depots, and seing the prevalence of 14.5mm ammo in novorussia, a few ZPU for multipurpose and anti helicopter warfare is not asking too much. Static mounts well hidden, to protect heavier AA guns, and mounted on pickups, UAZ, trucks, etc...
KS-19 is a 100mm gun (using T-55 ammo), working in batteries with radar, it would be a punchier but less agile asset than the AZP S-60. 100mm ammo are found in every depot of former soviet union arsenals, so, useful, and the gun would be a deadly asset to protect key sectors vs ground threats. The 100mm ammo in question is different than the one used in ubiquitous MT-12 smoothbore guns, just in case one didn't know.
the M1939 85mm or 52-k, is a WW2 vintage gun, still used after the war but totally replaced by KS-19 and AZP S-60... I don't know what could be done with them, but a 360° quick firing gun is never a bad thing. Only useful if 85mm ammo can be found.
SPAAG: 50 to 80 SPAAG would be great, most of them should be shilka, but a few dozen could be ZSU-57-2. Tunguska or pantsir missile-gun duo, well, it could be possible, but in very small quantity, russia must give them... And I recall of one tunguska captured in the late summer 2014, no? All mounted AA gun are listed as artillery rather than SPAAG, so i think that's all.
manpads: the more the better, using teams of specialist in highly mobile light trucks, is the solution. I'd say 500 to 1000 IGLA or why not older STRELA are a must have.
SP SAM, already a healthy dose of strela mtlb/brdm captured, a few OSA, and surely a pair of BUK, well, more of those. Russia could deploy 2 S-300 sites, one right at the border of novorussia, so it covers all novorussia, and one in crimea (already done probably) to enlarge the coverage zone.
With such a dense combined air defense net, only US airforce could operate, and only if they are willing to lose up to 50% of what they deploy. Ukraine airforce that was litterally decimated in summer 2014 by a few manpads, would stand 0 chance against combined means, radar of different kinds, and simply so much firepower.
Novorussia having an "airforce" would simply be a reason to lose precious time and money. Let them western smart boys have airforces, let ukraine dilapidate all its non existing money to rebuild its airforce with NATO crafts, and enjoy the firework if those fool dare fly over novorussia. Their precious latest tech F-16 of newest model (which is probably what ukraine will try to buy, or if not, a grippen or the old french mirage 2000 recently replaced by rafale) will stand no better chance than a primitive and robust SU-25 against hard hitting artillery saturating the sky guided by accurate radar data... Or better, let's see how the vaunted A-10 will fare.
novorussia military and defense priorities:
1: strong and competent leadership (more or less already achieved)
2: strong and well equiped mobile infantry, in big number (more or less achieved)
3: knowledge of terrain, defensive positions, in deepth defense lines, control of key roads, crossroads, ability to hold ground and build entranchements (rather good)
4: intelligence units, drones, accurate map data (good but improvable)
5: strong artillery working directly with intel units, to suppress ennemy units and ennemy artillery (more or less achieved)
6: anti-tank means of all kind, RPG, ATGM, mines, artillery included with or without submunitions, less important but still, AT guns. (close to perfection)
7: anti-air means of all kinds (need far more number and a good training, leadership, own branch of the army, etc, but seing how ukraine air force no longer exists, it's ok as it is now)
8: armoured units, tanks, BMP and others, to lead assaults and have the initiative on its side (growing, but already nice)
9: building a large and redundant park of vehicles, trucks, uaz, and why not civilian cars if they are good enough.
10: establishing multilevel repair and maintenance units, depots, and factories, (already good, needs improvement)
11: stockpiling ammunitions, weapons (firearms, AFV guns replacements, etc), establishing routes and procedures for effective supply to the frontlines.
12: same thing with food, military uniforms and gear, etc.
13: professionalizing the army, getting rid of all problematic warlords and simply bandits, punishing those who comitted crimes against the population, getting rid of foreigners like chechens or people having no business in novorussia at all, or either make a sort of very controlled "foreign legion" to control all those who came to fight but can become a problem for the society.
14: building military infrastructure, bases, establish strategic and tactic positions for key assets: command posts, artillery, etc.. Build serious training centers.
15: establish military salaries
16: (should be before 10 in fact), large amount of communication means, probably russian radio stations would be the best bet (old models).
17: uniformisation of insignias, formal creation of brigades who created themselves a name during the war, like somali, etc... Adoption of a uniform, could be based on the cut GORKA (seems pretty much all novorussian fighters either have or want to have one, confortable, ideal battle dress), with a uniformised camouflage pattern... National insignias for all members of armed forces, etc...
and long after numerous other things, you could say "creation of an airforce"...