Let's assume mid-era, as there are a lot of late-era mods already. Don't the Finns have something of a reputation as sorcerers among their neighbors, Kelavala aside?
I'd drop the Vaetti, or make everyone Vaetti.
This is my suggestion for magic paths and special powers.
Witch (everywhere) - EN,{FWE,75%}{FWN,75%},healer 20%,prevent bad events 10%
Spellsinger (everywhere) - F2N2,{FEDN,100%}{FEDN,10%}
Shaman (capital only) - Sacred, turns into a Bear, maybe even a werebear (thugable), E2N2,{FWEN,10%}
Sorcerer (capital only) - D2WFN,{FWDN,100%},{FWDN,10%}
Another option would be to convert some of those heroes into commanders - so the witches could have air magic and *all* turn into giant eagles; the sorcerers could all have forge bonuses.
I sure hope they add more nation slots
