If you have the skills to do it, I guess it's possible to achieve. I might (personally) weigh the cost and annoyance of the USB port in comparison to how long your battery has been around. It may be simpler to replace with something else (and possibly not a USB internal charge battery) rather than try to fix what you have, only to have the battery die on you a few months later.
But, if you have the skills and want to do it (and it's achievable in your setup, which I know little about) there's not exactly anything WRONG with doing so, I'd guess. And, you'll gain skills doing it if you haven't.
I'd only ever consider trying to (well in my case, getting the husband) to switch one out, and even he might have a little difficulty, I'd think if it were something like a radius, which I can't replace an IS a removable battery
device that was recommended by the manufacturer to charge via USB. With that said, sometimes the run time on an internal battery can surprise you, I have an Innoken setup like that an ECF member gifted me and it's fairly old and well used, but still functions like a champ.
Good luck with whatever you decide
Anna
