Well, all of this is subject to adjustment on the fly, but my initial thoughts on the matter are:
We'll start the match off in a Light, Level 1 (Intro tech, or whatever its called these days) with a 4/5 pilot. When you perish, you can pick to bump up your weight, your tech, or your skills. So, a Level 1 medium, or a level 2 light, or a 3/4 pilot. As for how to randomize it, I figure I'll let people either express a faction preference, or just go with random. if they go random, I'll roll a die and pick a faction based on that. if they have a preference, I'll use a RAT for that faction.
I was also thinking it'd be fun to do some themed rounds like "Everyone pick a mech you really want to use" or "pick the mech you hate the most" or perhaps "shitty autocannons only!" I'm open to suggestions for other themes, too.