I guess it wouldn't hurt to try, except that if it's less than a 50/50 chance I'll get a working battery out of it (2 years old and sagging at that), then I don't want to invest the time, I'd rather buy a fresh one.
I never found a decent HK LiPo that would fit (all 1300mAh or smaller - 2200mAhs were less than 5mm too big on one axis).
Inside the Ryobi original battery, there's a frame that holds 5S2P 18650s. I'm tempted to fit 10S1P of LTO 18650s into it. Will only get 1300mAh into it, but it would be great for small jobs that need a lot of power and rapid charging. I can get a 15A charger, and have it recharged in 5 minutes or so. 24v @ 19.5A continuous.
eBike: Q100H on 16S with Phaserunner FOC Controller
eMotorscooter: Vectrix VX-1 on 36S
eCar: Mitsubishi Outlander PHEV... Waiting for warranty to expire
eHouse: Still on grid, but with LTO batteries and 3kw LF inverter...
After 5 builds, the best advice I can give, is start with high quality products. I prefer http://www.ebikes.ca