Originally Posted by
MiPeGr
Would that mess with shifting? Either with the deraileur due to the big # of tooth jump between middle and inner, or with the ramps and pins?
That is certainly a possibility. You would need to see what specs your FD and RD have and what they will handle as far as capacity and tooth jumps.
If you have a coop in your area, there's a good chance you can pick up a chainring (even all 3 or a crankset) dirt cheap and try it. Might need some FD adjustment or tweeking.
You can certainly replace the crankset with one of those mentioned. Most likely this will require a new bottom bracket compatible with the new crankset. The crankset determines what BB you use. The variables will be frame interface (PF, threaded, HTII etc), the length of spindle required to create the required chainline, and the interface on the spindle to crank arm connection (sq. taper, ISIS, octalink, HTII etc). While this may sound complicated, it's really not that bad unless you really start trying to mix & match things.
A new crankset with the smaller rings on all 3 WILL require the FD to be remounted and adjusted lower.
Do a little research regarding BB, chainline, derailleur capacity and you'll get an idea of some of the things to look out for.
Good places to look are Sheldon Brown, Park tool and some of the Shimano tech docs.
https://www.sheldonbrown.com/
https://www.parktool.com/blog/repair-help
https://si.shimano.com/#/
Celebrazio: Bicycling - Shimano Road Bike Parts Compatibility