I actually think shadowland will be the perfect time. I mean it's all shadow and control and whatever, what better to build big ol machines that can't be mind controlled and aren't afraid of dark powers to end the powers that be?
Plus it'll be the first time the "Mechs" be anything more than a toy. Throwing bombs and little gadgets sounds super fun and honestly wouldn't really need that many new mechanics to pull off.
Mech suits would be like druid's different forms, and bombs/grenades would your regular spell casts or time delayed instant casts.