Any suggestions for caliber without changing the bolt or altering the bolt-face?
Without modifying the bolt, or changing it out, you're "limited" to the dozen or so rounds with .473" case heads and about 2.810" loaded length. Some variation in overall loaded length may be possible, less then 2.8" won't be a problem, longer, might be...
This essentially includes the entire family of rounds based on the .308 WIn case, both factory and wildcat. So in factory rounds that would include the .243 Win .260 Rem, 7mm/08 ,308Win and .358 Win.
Really the first step you need to do is decide which kind of rifle you want that action to become. Long range match rifle? Light weight stalking rifle for big game? Short brush gun for thick woods hunting, dedicated varmint rifle? Something in between? Some overlap?
Do you want something like a 26" barrel 6.5mm something or other, for long range accuracy you can do that. Or you could build an 18" .358 Win for easy carry in thick woods and heavy short range punch. OR something in between.
Decide on the general purpose for the build, THEN look at which calibers will perform best for what you want, and THEN look at what features the rifle needs to get that performance.
THEN, we start looking at the actual build...and budget...