So I wrote my own set of 'One Page' Mecha combat rules for use with Robotech.
(don't bother trying to read the pic, just download the rules below)
The concept is that they are short in length (one page), no book keeping (all you need are wound markers), fast play, easy to learn, and can facilitate combat on a mass scale (100 figs). Just print off the rules sheet with the army faction page on the back. I prefer to laminate mine for durability.
You can download it here: Mass Mecha Combat Rule
Give the rules a try if you want, and send me some feed back as it needs play testing.
* Fixed link to updated rule set