I have a couple of those little 1/2 hp or so 4" belt combo sanders. I like them, and they work well for what they are. When I was looking at how to do a template sander, this was a consideration I had. Pros to this include belt price, general machine cost. Cons are the HP side of things.
Ironically, my big 80" edge sander recently started having motor issues the very second I finished my template sander for it. So now, I still have no edge sander, and this sort of thing is back on my radar. I'll be following this!
One consideration I had for the bearing portion was a simple pin in the table, as you may have heard of, rather than a true bearing or bushing guide. Now having to disassemble my set up & take the motor to a repair shop, this looks a lot nicer than before because it would be ridiculously simple to set up & alter if needed. Have you thought of a pin?