I have owned a lot of shelters including a similar to the Stratospire 2, Six Moon Designs Lunar Duo. The big advantage to the the Mountain LT is the price. For instance the Stratospire 2 costs 4.5 times as much as the retail price I paid for the Mountain LT.
Mesh extensions and a mesh door sound like great additions. I would want the mesh to be removable for use in snow. I would also rather use a strip of tyvek for immediately under my pad than have a floor. I always felt like I had to baby the floors of the few tarp tent style shelters I've been in. Floorless is much more conducive to my style of use. As for weight, no see-um mesh weights about .9oz/sq yard
If minor modifications make the Mountain LT work for others, more power to them. I think that it's great that there is such a robust and economical option as the Mountain LT. Now if there was only an earth tone color option.