Rebuilding an Li-Ion Tool Battery with Li-Po Pouch Cells (Ryobi P189)

[RukyCon]

So awhile ago, i picked up a used Ryobi drill from a thrift store, so I could give it to my father (so that he could have something that was slightly better than his Drill Master drill with a broken battery mount), but with that drill came a dead P189 1.5 Ah battery, since my charger refused to charge it, i decided to take it apart, I found that all 5 of the 18650 cells in the battery were discharged to less than 0.5v, so knowing that the cells in it were pretty dead, i ended up setting it aside, unsure of whether i would repair it.

Anyway, about a week ago, i dug up the battery again, and this time wondered if i could rebuild it using Li-Po pouch batteries instead of 18650 batteries, the main reason being that i don't have any tools for spot welding nickle ships onto the cells, and i hear that soldering the cells may damage them, so after doing a bit of measuring and looking around online, i found these batteries that seem like they should work without needing to do major modifications to the battery housing (i am a bit skeptical of their rated capacity, but as long as their over 2000mAh, i would be happy).

Now i do have my concerns with the project, mainly revolving around possibly drawing too much current from these cells and causing them to puff up or worse, so i thought i'd ask here and see what any of you have to think about this project, and so i could be told if its a bad idea before i try pulling it off, tahnks.