Reciprocating sander - video

[Frank S]

Still a fair bit of thinking involved. And he pulled it off well enough.

Yes, he did, were there parts of the build which could be improved on? Sure there were, and a lot of that depends on how much time effort or money you want to throw at it, and he may find that he wants to do just that now that he has proven the concept, If things were always built perfect the first time around and there was no follow on improvements or changes which could be made, we would all still be driving cars from the model T era, though some of us would argue, myself included that a lot of things put in cars today would be better left out of them.
Any reciprocating device such as this sander is going to have areas of limitation especially if a table or fence is used or required. It is worth noting though when he had it in the horizontal mode he was able to utilize about 80 to 90% of the surface area