3 other boats recommended for the solo/tandem options - The Mad River Malecite, The Wenonah Solo Plus, and the Bell Northstar.  

You can add a center seat to any of them, or install a kneeling thwart if you prefer.

If you want to paddle a tandem solo, backwards from the front seat rather than from a more center position, you can do what you want with any boat.

The Bell Morningstar and the Old Town Penobscot 16 are good candidates from that perspective, and both can be had in royalex if your rivers are rocky.  

It sounds like you are looking more for a river boat than for a lake boat, and if so, then look at the rocker on the boats - you want a more manouverable boat.  If you are looking for a boat to also be used in BWCA style lake tripping, I think you can get any of the boats I mentioned in a Kevlar version, except the Penobscot?

I just took a look at hte Mad River website - Mad River has kind of refocused on canoes, bringing back some discontinued models.  The Malecite looked pretty good for your stated uses - 51# in Royalex - I guess they don't make them in kevlar anymore, though you might be able to find a used kv somewhere.

I have a Northstar as my tandem lake boat - I've only soloed it once, kneelin using the thwart.  It is not a good boat to use paddling reversed from the front seat.