| you'd probably want/need a strings gauge set that is atleast, or close to, 35-50-70-90-110-130.
Tuned ADGCFA#, I don't see why you couldn't keep it in that tuning while the guitars play in drop C (CGCFAD); what i have done in the past and what I've seen/heard other players do when guitars play in a drop (lowest string down one step) tuning, is as long as their lowest open string is on the 3rd fret of your lowest string it shouldn't be too hard (sometimes easier) to play the parts.
For example, I used to play in a band that played in drop D (DADGBE), (obviously everything explained here would apply to you just the same just one step lower) but as a bass player I don't really like playing in drop tunings I guess that kinda comes from my jazz experience in highschool. I exclusively play 5 string basses (BEADG) for the past 11 years, playing the guitars low D on my third fret of my B string was not difficult, in fact most said and I agree that the low D on the third fret of a B string sounded thicker/fuller than a low D on a drop tuned 4 string which is what their previous bass player did. There kinda are pros and cons to this method, but for my playing style it seemed more to my advantage. Ya kinda have to get used to a bit of fretboard acrobatics and skipping strings, but like I said it wasn't that hard to adjust to and ya get used to it.
BUT if doing that doesn't seem like it'd be your style or something you can pull off successfully, then I don't know think going back n forth D to C will damage yer neck, you just might have to get pro setups more frequently. Maybe you might want to get a 115 gauge for your second low string which might be a bit better for intonation of going back n forth with that OR maybe you can get another truss rod installed on that bass if possible, which could be pricey though might be worth it to you.
I hope what i've explained here is helpful in some way. Good luck. rock n roll. | 
