Real fun in MekHQ where you have the same rated engine for 3 different ASF tonnages, 2 'Mech tonnages, and a vehicle. all of which stack individually.
It's also close to insane when the program has to support 'Mech body parts for every tonnage and tech type, both bipedal and quad. Scrolling down the list of 200+ parts in the "Purchase Parts/Locations" sub-menu to find a Left Arm for a Phoenix Hawk can be a frustrating experience. Normally, I'll simply order it from the Repair menu, but if it took a Shoulder hit, you have to scrap it to order the replacement, leaving your 'Mech with no arm at all until the part arrives. Better to have a near-useless arm to soak up damage points than to scrap it and have everything automatically transfer to the torso side.