Wheelchair bound modeler layout ideas??

If he can move around in his wheelchair, some kind of cantilevered benchwork might good.    Put is at the height so can roll his leg and chair under and get up close.    As you say maybe 18-24 inches deep for arm reach.     It could be a shelf along the wall, or an island with the benchwork hanging out way beyond the legs.    I think it is easier to hang it off the wall like a shelf.    It might even be possible to buy big enough shelf brackets to support it.    Otherwise you need diagonal braces periodically from the front down to the joint where the floor meets the wall.

Tom, what a great friend you are to take the initiative to help a friend in need! Well done!

I would talk first with his Occupational Therapist (with his permission) to determine  what therapies are most effective. Repetition of lost skills often bring those skills back. For example,  give him tasks requiring the repeated use of screwdrivers. At first it will seem impossible, but with repetition may gradually improve. Let him screw track into layout board until the cows come home. Or give him a 2" paint brush and let him try to hold and to control the brush well enough to paint the layout surface. It should get easier. Just keep him away from things like soldering irons, sharp edged tools, and pointy things.

I would be looking at a long stretch against a wall with a loop on either end, something he can wheel under, not too deep, and that he can work on comfortably.  If he will be bed ridden in the beginning, get the track and base up and let him use a LionChief remote.  Once he progresses, he can start to fill in the details 

Thank you, however this is two rail,  no looping in mind.  Also of consideration, this residence is a rental so wall fastening in not an option.

Has anyone dealt with this situation themselves?

I would think that a Timesaver like layout would fit the bill.  He can expand it to whatever length he desires.  An eight foot table that is at most 24 inches wide will allow him to get his wheelchair underneath with minimal interference from legs.

Jan