Welcome aboard Reddog. You should enjoy owning a Triumph if you weld plastic.
There wont' be anything you can't do with these boats. Seriously though it is very easy to fix scratches and gouges (when you hit the dock and scrape across something) by using roplene welding rods. I'm working on a Maintenance and Modifications DVD that shows how to do this by folks at the factory and at my dealer, Merritt Marine.
Yes the insert will fill the void but I hadn't actually thought about welding it in. I'll pose that idea to Triumph and see what they say. Only boats prior to May 2005 would need these plastic inserts though. On my first Triumph I actually used a modification that another member here suggested and used the deck plates to be able to screw them off and vacuum out water from time to time. But sealing them tight and not having to worry about it at all is a much better idea. I'll let you know what I find out.