yes it's quite possible that a ship could have multiple smaller reactors instead of a single massive core.
However it should be assumed that economies of scale outweigh the benefits of redundancy, ie a larger warp core operates more efficiently than two smaller cores.
Didn't the Constitution-class U.S.S. Enterprise, NCC-1701, have multiple warp cores, as seen "behind the grille" on multiple occasions in Engineering? ProfessorTrek 19:25, August 17, 2011 (UTC)