As a bassist and guitarist who has been in a few bands, I suggest this:
Using drop A would mean you should use a bass string that's 75 gauge on the low end of the tuning.
Maybe throw in a couple more bass strings for the E and A, downtuned from the standard bass gauges for G and C. Off the top of my head, you could get away with a 40 and a 30.
It's the seventh string that gets a bit muddy at lower frequencies but for drop A that would work.
If you have two guitarists, this could go a few ways.
Idea one:
Have only the rhythm guitarist use the deepest strings.
They'll double as bassist.
Idea two:
Designate the makeshift bass playing for the lead guitarist when they're not soloing, therefore allowing the rhythm guitarist to fill out the chords.
Idea three, less focused
Equip both guitars with the low strings. Feature solos with either bass or rhythm guitar backing it up.
I don't recommend this as much because something will seem missing.
Hope this helps.
~Aizen