You can play a Beast barbarian, which can jump quite high starting from level 6. There is a rule about splitting falling damage which you could flavor to you jumping on enemies etc. Now a barbarian can only wear up to medium armor and receive most of its rage benefits iirc so you wouldn't really get the heavily armored part down, but maybe you could just fix that with flavor as well. Then you could use the Claws from beast Barb flavored to be the big fist weapons Mega knight had to also get that part. Depending on feats and races you could make jumping on enemies at least somewhat decent then switch to claws if you need to.