Personally, I'd avoid giving the UBW any kind of cloaking capability. As we saw in WC4 the cloaking Avenger was a one off plot device, not something that would be reasonably repeatable (even with Kilrathi assistance). Additionally, the cost of mass producing cloaks and then retrofitting existing fighters that weren't designed with stealth in mind would be pretty onerous. In-universe we see that ships with cloaking tech are specifically designed with cloaking and stealth in mind, retrofitting cloaks most often wouldn't work as expected.
In my mind the UBW is more of a Zerg-rush type faction, they can overwhelm you in the early stages with tons of cheap and expendable fighters, but will struggle in the later stages of the game as more technologically advanced factions (ie Confed and BL) gain their super-tech ships like the Dragon and Excalibur.
Speaking of the BL faction - I know the mod currently defaults to giving the faction the BL carrier as a default. I was thinking that they should start with Rangers and Concordias (since they're basically Evil Confed) instead and have to research to get the stealth carrier. Let's face it, a cloaking-capable carrier with a wing of cloaking arrows, Dragons and Excaliburs is fairly OP, and starting out with something like that might throw off game balance - and that doesn't take the Vesuvius into account.