If the test pads (5V) does not have protection then adding a small fuse to the 2.5mm plug base should not be a problem.

As for my system, it is sufficient for me since i have 20+ 4.2V sources/power supply's, else a 5V - 4.2V (with charge controller) chip does not take up much space, i have many laying around from the EGO-T E-Cigs i order home for people, they come with an actual LiPo/ION charger that takes 5V 400mA (USB 1/2 Limit) and have an indicator light to show when battery is at 4.2V, but this is just an example.

But having another method of charging is still very good, i on average use my USB one time a week MAX.

I have been thinking of upgrading my setup with some copper lanes (flat copper...) in the top of the cover to the 2.5mm and then some lanes on top of the battery, so when the cover is on the battery is connected to the 2.5mm, this is just to eliminate the wires that attaches my Dual Scud to my cover