I believe we’re planning to release new end caps for the 4" and 6" enclosures quite soon that will include holes for M14 penetrators. You can also get a blank end cap if you want to make your own holes - whether the electronics fit depends on what you’re including in the enclosure you choose.
We’re developing a 6S battery that will fit in a 4" enclosure, which should hopefully be releasing towards the end of this year.
You can install as many lights as you want, assuming you’re able to supply sufficient power to them. Note that if you’re wanting to power them from a single set of wires, there are limits to how many can go in one daisy chain.
It’s not something I’ve looked into. There may be some other options that have been discussed if you search the forum for something like “larger lights” or similar.