I fail to see how 190 mass for 1100 damage is good at all? 190 mass worth of medusas do 1150 damage in a single volley, and they are just a t1 unit that doesn't require a T2 HQ to produce. 190 mass worth of anything will probably do more than 1100 damage during its lifetime. I don't see how firebeetles are good for killing mexes either since it takes 2-3 of them to kill one t2 mex and they probably need to be dropped there with a transport. You are pretty much always better off dropping medusa to snipe stuff, even if they are the worst arty for the job, since they do more damage in just a single volley and will likely be able to fire multiple volleys.
This is all based on the current state of the firebeetle, which does very little damage, but if it were buffed to do a lot more damage then it would just be back to the old beetles that were supposedly op before I started playing FAF. I believe that anything that makes the firebeetle a better choice than TML, arty drops, corsairs, or gunships will inevitably make the firebeetle overpowered because those units are already very good.
Static stealth generators have a pretty clear role of stealthing things (it is in the name). There is nothing else in the game that provides that role. It is mostly useless due to the way fog of war and stealth work, but it is still a unique and occasionally useful ability. Firebeetles do have some roles as well, they are just so outclassed by other units that do the same role that they are pointless. I'm very skeptical that they could ever be a good choice in the Cybran arsenal while also being balanced and fun to play against.