I'm sorry if I had misunderstood you, but doesn't mIRC already have 1?
autosize can be annoying, some networks allow 30 char nicknames, imagine that big nicklist
And why do you need mts?
I'd prefer a section in (display) options where you can edit EVERY part of an event - prefix, message, nick, address, suffix, additional message, colors and more and more
I use something like this, and personaly i prefer it to mts
I support 3 and 5, but if 5 means customizeability, not just another builtin non changable *-based theme