If you don't want a five, you can always tune your second bass down to something like B-E-A-D. That'd cover all of the low tunings and stay on four strings. There's no need to tune up to play songs in a higher tuning. Just play a bit higher on the neck. A capo can help if you really need the open strings on certain notes for certain songs.
There's also a bass whammy pedal that transposes notes up or down so that you don't have to retune. I've not used one and therefore cannot say how well it works. But it seems like it was designed to address the exact issue you've described.
My opinion - Let the guitarists do whatever they're gonna do with their instruments. You don't have to follow their lead on retuning instruments.
There's also a bass whammy pedal that transposes notes up or down so that you don't have to retune. I've not used one and therefore cannot say how well it works. But it seems like it was designed to address the exact issue you've described.
My opinion - Let the guitarists do whatever they're gonna do with their instruments. You don't have to follow their lead on retuning instruments.

