Track templates are working well so far. There are a couple of things to watch out for though.
At first, I tried to put all tracks (disabled) into one project, but I found when I dragged a track to the arrange window, S1 ran through a very long 'search' of the template song each time. So I broke each instrument group/library out into their own template. I placed them all in a tab in the file browser.
Dragging a track (or multiple tracks) over is now instant.
Secondly, using this method doesn't allow me to replace an existing track by dragging another on over it. That's no biggie though.
Hopefully they are able to update this feature so it would be possible to drag tracks in between existing tracks. Much like you do when dragging instruments, audio etc. at the moment imported tracks land at the end of the tracks list.