I'd say almost anyone can make it that far if by 'just working at it' you mean giving up nearly everything else to achieve that goal.
and there are plenty of cat2 only stage races around.

I'd buy a few cassettes. 12-23 or 11-21 for flat rr's/crits, 12/25 or 12/27 for hilly rr's depending on how well you can climb. My 12/25 gets the most use.