On your cordless phone problem you still have to deal with the LVC issue, but 1 could easily replace them although you might want to try a different style something like the one in this post:
They are about 1/4" longer and about 3/16" wider than 3 AAA cells. The same length as a AA and the thickness of a AAA.
Jeff
The Warnings & Cautions discussed in this manual cant cover all possible conditions/situations. It must be understood that common sense and caution are factors which cant be built into this product.