Those ComStar mechs are Star League designs and can still be found (if rarely) in House armies, so really the only ones you wouldn't use in 2950 are Clan units.
Somewhat.
I have a Raven, which is a NEW mech from 3039 from The Capellan Confederation.
The Hatchetman, which was brand new in 3023.
The Annihilator, which was exclusive to the Clans, and specifically introduced with the Wolf's Dragoons, who had it built locally in the Inner Sphere in 3048.
A pair of Exterminators, which I could use, but I prefer 3025 tech level. The official lore is that the only time the Exterminator was built in normal, introductory/level-1/3025 tech was a brief stint in 3007.
Anyways, I could just ignore all of that and use them anyways. Technically, they are regular, 3025 tech variants of them all, but I would need to be playing in 3025-3039 era, just before LosTech was rediscovered.
I just can't bring myself to do that, so I bought a pair of boxed sets to fill out my ranks to get to the magic number of 40 Inner Sphere Introductory/Tech Level-1 stuff.
Again, my prefered year to play is smack-dab right in the middle of the 3rd Succession War. 2950 AD.