Well, actually I don't have problems with mini-mechs (those under 10 tons).
The mecha from Battletech are a little bit better than those of Japanese
animation, from a reality standpoint. However, unlike the creators of
Battletech, I don't really ever see mecha being much of a combat factor. They
are slower than tanks of the same tonnage (usually) and cost too much more
than a tank. The only real advantage they have is mobility. However, when
grav vehicles come in, this is cancelled out (granted, a grav vehicle
is even MORE expensive, but it makes ground-contact vehicles very vulnerable).
Really, mecha are good at about TL8-9, in light tonnages (5-25), serving
as scouts, recon, and highly mobile fire support for ground troops.