Unfortunately you're still going to have to climb up those stairs at the Land Transport Office whether you use an agent of not. That's where you have to go to pay the fee, have your photo taken, and the license issued. They have never done anything to provide for people who are handicapped. They don't even have any designated handicapped parking spaces - at least none that I noticed.
It would be nice if a new office opens up - one much closer to the city (this one is 11km - 7 miles out of town) and much larger to handle the large numbers of applicants who show up every day, much more modern - and with a lift if there is more than one floor. Of course, no such building is in the works, but maybe one of these days.
In any case, if you are going to use an agent I think many of us are looking forward to your report and, of course, which agent you used and their fee.