I think you guys running some lighter, geared motors and your large spoked wheels would seriously be fine on an aluminum frame with a torque arm backup.
You would really need to make sure that your torque arm is really snug on the axle, and then FIXED by going a bit overboard with hose clamps would probably hold up pretty well
Using something that I made for my steel frame like this is probably a big no no on Aluminum:
Topic^^It would just snap the entire dropout aluminum weld and puts more stress on the joins - complete opposite on the steel frame dispersing the torque across the plate, bolts, and weld joins
On the aluminum frames, it's really the thinner front dropouts that are the biggest culprits.
The rear might fail, but it would just spin the axle in the dropout causing damage to your wires. The biggest problem on the rear is actually hitting a gutter/pothole at speed or any large forces like doing a jump and hitting the ground will be the hardeded axle that will physically snap the dropout.
I see a heap of guys that swap out the rear assembly for a steel one anyway. So maybe keep an eye out for a replacement steel rear end. Alot of bikes are built in the same frame design in both steel and aluminum. That would be ideal !!
Funny, last night someone had an Intrepid 24" Steel MTB they kindly left out for hard rubbish. So yup I sure snatched that up! Its doesn't have front nor rear suspension but the frame and tubing is pretty serious. Only a bit of surface rust so its an easy fix
This prompts me to create a new topic for ideas lol..... Ok you can have your ears back now, I think I've
'torqued' them off !