One other opinion on the musicality of a low A. I had a 5 string bass about 35 years ago, and....ended up moving it on. Back then, I was playing through typical bass amps, which didn't reproduce the low B at all - even the low E on standard tuned bass isn't really well handled by standard bass rigs (then or now). Sure, with a high pass filter, you can get the rig to tolerate that note, but it won't (at any decent volume) actually produce the fundamental of the note - we have "discussions" on Talkbass fairly regularly as to whether or not the fundamental is important - I'm in the camp that it is (explanation to follow). Bass amps aren't actually designed to produce full volume really low frequencies - they're designed to be light, loud and portable, and in that trade off, low end extension gets cut. If you want loud and low, you need to give up portable and light.
Recently, I've built my self a 5'er, and am working on one more (I build all my own basses). Why did I change my tune at this point? Because the majority of gigs I play, I don't use an amp. I hear myself through in ears, which can reproduce the low B on a 5 string, and the places I play have PA's that do just fine reproducing the fundamentals of a B. If you have the opportunity to play through such a rig, you will understand why I think fundamentals are important - when done well, they make a big difference.
So, my point is....tuning a 5 string down even further, don't expect to get massive low end out of an amp - if the bands and places you're playing in are going to cover the audience with sound from your amps, the results may not be as impressive as you hope. If, however, there's a good sized PA involved, things can be quite different. That doesn't mean you won't be able to make music with the bass you're pondering, just realize there are limitations when amps and cabinets get involved.