I believe they use the tp4056 charging circuit. So it is fairly safe.
With what is available at the moment I would say charger wise you won”t beat the Liitokala Lii-100, charges Li-Ion & NiMH, $4 & also works as a power bank.
Light wise again with what is available at the moment, Convoy S2+ or C8 or Thorfire C8s.
That leaves you plenty enough for cells.
Things might change before the year is out though but I have all of the above & can”t rate them highly enough for the money.
Indeed and its a few dollars cheaper, at Mountain one can get
$11.55 Convoy C8
$8.65 Sanyo 3500mAh
$6.49 XP-L V6 1A
$4.20 Qlite 3.04A
$4.90 XTAR charger
$5.50 test and build
———-
$41.29 each plus tax/shipping
Perhaps a volume discount if buying many lights?
The OP can get other lights cheaper, Simon sells Convoys and i believe he offers limited customization, and better tints will be available with the 9 months the OP has.