There appears to be many different solutions for transporting wheelchairs and scooters.
There would certainly be the consideration of cost with any of these solutions shown in the attached video.
I am trying to image the process of getting a scooter into the bed of an Avalanche.
Without some sort of lift, I am having a difficult time seeing any way other than to use some sort of ramp.
It will take a fairly long ramp, I would imagine, to not be too steep to safely drive a scooter up into the fairly high bed of an Avalanche.
Then, there would be the task of moving and stowing those long ramps.
Seems to me, if affordable, the solution of the rear, hitch area mounted lift and a cover to slip over the scooter would be easier than driving a scooter up into the bed and then dealing with the ramps.
It will be interesting to see what solution you finally come up with.
Best of luck.