I tune standard.
Honestly, if you're going to try to have open strings for all flat keys, there's no end to that... Soon enough you'll run into a song in the key of A flat, and then you'll want to tune 3 or 4 half steps down... I guess some people just add more strings, which is fine. For me, I've decided that low B is enough for me. If I have a B flat or A, I just play it higher, nothing wrong with that.