Funnily enough, I have (and have posted them here previously) made designs based off Armored Cores.
Keep things around 60-65 tons, and be willing to use Hybrid mix'n'matching, and it's actually quite surprising just how WELL you can make one mimic a Core down to the last detail.
Yes, even the ones with the Overboost 'I'm standing still. BOOM! Now I'm going Mach 1, three inches off the ground' type shenanigans and still have them be able to swing a 'laser blade' around (retractable blade + flamer + TSM + Supercharger). It can quickly get hilarious if you somehow find a way to cram in a Partial Wing.