from someone who tunes to drop B or B standard on every one of his guitars, I can definately say that scale length does not play a significant difference when volume is cranked! A common misconception is that a longer scale guitar will add a noticable amount of string tension...I would say no. Not any you can notice anyway...you see when a string is longer, it is easier to bend, which in effect makes it feel looser to your fret hand than on a 24.75 inch scale (your les paul). The tone will be clearer and have a bit more attack, but will lack the low end thump of a shorter scale. Both are good for what they are, but at the end of the day, I can't tell the difference when my volume is cranked to eleven.
as for string gauges, I use 12-16-24-34-44-62 for drop B on an esp eclipse ii standard (same as a LP studio light basically...) so I would step each one those up for drop A# tuning (which I have done before!). Something like 13-17-26-36-46-66 should do just fine. Also, many think in flames uses 13-70, but they don't! I have asked them personally and they use Elixer 13-65, as mentioned before...
good luck and hoped this helped!