1. You're suggesting to balance Clans and IS by the quantity of mechs from each side. Sounds good. Say, 9 vs 15. Why not?
Because where the hell are you gonna find 15 IS mechs against 9 Clan mechs for every single match???
Hordes of people, who like Clans/who don't have guts to fight in a weaker mechs are going to wait for ages while matchmaker is trying to find those 15 players, who are brave enough to be a part of a pug team, which does not have a clue about "Stick together and focus fire" in 90%.
Sounds cool.
2. If you ask someone, no one wants to aknowledge, that they care about kill death ratio. But even though it's just a statistic, these IS fighters will have much less occasions to get this satisfaction of killing a mech, while a good player in "unnerfed" heavy/assault clanmech is going to wreck half of IS team every round.
3. Clantech provides a lot of superabilities. It's not just a high pinpoint alfa strike. Clantech LRMs working from 0 to 1000m are gonna wreck any team of IS mechs, no matter how many mechs you put there. These things should be nerfed without a question. It's not a table top game. It's a multiplayer shooter, so every weapon should have it's downsides and countermeasures. Current IS equipment cann't provide this countermeasures.