Wheelchair modifications

[Wheels]

Hello first off.

I've been into R/C trucks for a while so I know a little about things but I need help from you Battle Bot guys/gals on this one.

I'm in a wheelchair, I mostly use a manual chair but got a Pride Blast 850 to play with, well I never did think it performed the way I wanted it to in the first place, the thing I didnt like about it was the power ramp up or what ever it's call'd. If I was in soft dirt and try'd to get out and gave it full power it just sat there like a bump on a log, it had to move before it had any power, the faster it went the more power the controller gave it. Safty I know but not good enough for me. When I push the joystick I want it to move or get stuck ya know. Well now I have over heated it to many times try'n to get out of easy obstacles and the speed controller has went south, it's out of warranty and a new controller cost like $600 and will be the same ol piece of junk I had before. I want more !!!

It has a pair of BIG 4 pole motors, a pair of 12v 80ah batteries.
The controller it has now has 5 settings for speed and power output.
If I had a controller that ONLY has one setting and uses the joystick for all power out put and speed thats ok with me, I'm 35 years old and rid a 100 hp Kawasaki ZRX Trike, I can take care of myself and my actions, say'n this as the wheelchair people wont even talk to me about any of this for liability reasons.

SO I have been looking at a few speed controllers that seem to fit the bill. Like the 4QD-150D. But I dont know how to make a battle bot controller work with a joystick for a power wheelchair, can I alter mine to work, what kind of stick would I need ?

This is what I want but need help making it work, Thanks for any help I can get.

P.S. I have my old controller out if anyone wants to try and make it work or mod it ?