I also like to add 2 things:
first, the spruances were build from the beginning to take the mk 26, there was even the never used option to rebuild them into kidd-style multipurpose destroyers later on.
second, the kidds were build for iran, which ordered perry's or mk 13 equipped kortenaers as well......... so we might say that in real life, both these systems were compatible enough to serve next to each other.
fact is also, that all designs except the kidds which had mk 26 were OR CGN's, OR AEGIS ships, both of which were not exported, especially not back then.
you have an ship with enough size to take the mk 26.... so why not?