Another way to play Mixed tech is to Multiply each ton of 3025 tech as 1.0, Star League/advanced inner sphere tech as 0.75 and each Clan as 0.5
So if you are playing a game with Basic (level 1) 3025 Tech against an opponent with Clan Tech and you have agreed on say 300 Tons then the Clan player only gets 150 tons of Clan Tech Machinary or 225 tons if using advanced (level 2) inner sphere. The Level 1 3025 player gets a full 300 tons!
Another way to determine the size of forces is for 2 players to use the Clanners and each bids off agaisnt the other.
So in a 300 Ton game both players build a unit and then bid off by removing machines and points of Elementals etc.
This should result in an interesting force of Clanner vs an Inner Sphere unit. (or even vs another Clan unit!)