RNG Armoury probably won't be on the next map, and for the population thing, 1 nukie per 4 crewmembers (Basically 1 out of 5 readied players) seems like a fine balancing point.
As for fucking with the spawn of the hardsuit/power armour, doing so basically fucks with a good deal of their combat options (There's an entire category in traitor gear dedicated to things you can put on that one suit) whilst also removing (arguably) half the fun of being an op. It's their best chance to stand on even ground against ERT who /all/ get hardsuits, with mounted laser cannons.
And Jackboot's got it nailed, the reason they hit the armoury is to give them the best chance of doing anything else without having to turn it all into a massive shootout where they /have/ to kill the entirety of Security. Back when the nuke ops were quite weaker on oldcode, they had to blitz Security's options to hope to stand any chance of surviving. This often meant surgical bombings of key points, such as Cargo and the Armoury.