I'm not in the 'TML is OP' camp (nor do I think it needs a buff) but I find it can turn teamgames into something of a coinflip, where if you or a teammate lets someone eco/tech up without being attacked then they can effectively lock you out of T2 by hitting your factories/mexes. this isn't OP or even strong outside of very specific situations, but I think there should be some opportunity for counter-play other than to rush t2 and get a tmd up. To that end I feel that dropping TML hp down to around where a faction's tmd is at allows for more options as you can get up a few bombers and take it out.
I made a test mod in the vault, with name "TML HP Rebalance Test Mod", or you can download it here. Sidenote: It seems to increase the number of missiles that a launcher can load, I don't know how to fix it. Oh well. I set all launchers to 1000 hp, making it take 3-5 bombers per faction assuming you only get one pass and no vet. I think this much or slightly less is fair considering it's still above the hp of most tmd.