Probably a bad idea, but why not include cloaking in all cybran presets? Stealthy engies for sneeky building or risky reclaiming. Stealthy rambo to shoot without being shot back, stealthy support option in whatever form that ends up taking. It fits in any situation just about.
As for what the support upgrade could do... I really hate to say it but a regeneration field fits them well, too well, even better than it fits Sera. All their stuff regens faster than other factions anyway, their nano repair upgrades have rediculious regen rates, they even got hives which are practiaclly a stationary regen field already, they lack mobile shields so they have an open slot for a mobile defence field. They even have a building that in the lore explicitly creates a nanobot field around it (Soothsayer).
It would not be an identical copy of the seras regen field as sera would also have the max health boost, but I can understand if the overlap is decided to be too much.
The other other things that make any faction sense are radar stealth field (redundant, although having a t3 deciver wouldnt be the worst thing ever). A cloaking field (extremely overpowered unless we give omni out like free candy). And EMP, which Aeon have nabbed first.
Edit: It has occured to me that personal cloaking with a radar stealth field would actually be highly versatile but not overpowered. That would be an excellent support option.