Ok, hopefully a few people will lend a hand.
What I would do for these, for what it's worth... Take Iran for example; google "military of Iran wiki". Read through the first paragraph from the wiki article, it will usually give some idea of what kind of Infantry type of troops they have. Pick either a special forces type or one they have a lot of.
Keeping Iran as the example, I'd take a look at the link that says "Revolutionary Guards." That would make a good replacement for an infantry.
So:
Iran-
Revolutionary Guards (replaces infantry)
+15% city defense