I'm sure it's possible to re-enable them, I don't know how to do it myself but I imagine it just involves tweaking a file or two. I doubt the units were removed as such, just switched off in the code.
Maybe one of the more seasoned DIY modders around here can advise?
EDIT: Zeibek, as far as I know altering unit recruitment for a faction is save-game compatable, in other words don't delete your Lusotanna saves just yet.
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