I’ve done similar mods in the past - here’s an example: Cheapo AA Flashlight Mod.
It’s a lot of work if the host is cheaply made. It would be easier if you just buy an inexpensive host from Convoy or Kaidomain since in the end you will either be paying more or spending a lot of time to mod the cheapo flashlight.
But I’m not saying you shouldn’t do it since I’ve found a lot of satisfaction turning these flashlights into something good.