A timeline for this kind of thing is hard as the first step is probably going to be research, so one thing that would be helpful is to have people find examples on the wiki of their faction's mecha (This is an easier step thanks to the existing list of mecha and power armors, though that may not be 100% exhaustive), and examples of RP where it was used by their faction.
To use Yamatai as an example, the kind of information I would want right now would related be the use of M11 Cammie construction mechs (though those might not have RP), the old V-1 Hoplites use in the pre-forum era (This will be hard), or the in-RP example of the old tale I was told about Yamatai buying a bunch of Origin mechs and basically tossing them at a planet.
For simplicity's sake, I will be excluding large power armor such as Kiries and Aggressors.