D-LI90 Idea

The D-LI90 is a decent battery but I think it could be better. It seems it would be possible to create a "battery tray" (for lack of a better term) in the shape of a D-LI90 that would accept AA's and it appears that two would fit. Of course, the only problem with that is the voltage would be wrong. However, there are 3.6V batteries in the AA form factor (or VERY close to it) and at least some of them are lithium as well.

So then, a "hollow" D-LI90 with a snap open/shut door on the bottom into which you could put two 3.6V batteries seems feasible or even just a simple and "permanent" D-LI90 "mod". Given the capacity of some 3.6V batteries I've seen, it should be possible to double (or more) the D-LI90's current 1850 to 2000 mAh capacity.