Finland, Czechoslavakia and Yugoslavia are ideas which come really often on discord in our discussions about modern era. We don't know how much it's doable, but seems really interesting ideas.
Finland is an interesting pick, but not especially for the "Nordic quality of human rights" things imho (it's more a "today" image of Scandivanian countries, mostly Sweden).
But Finland is interesting anyway for multilple other reasons.
I don't expect other european countries for the launch to be honest, almost all the big european superpowers have been covered. Two big european audiences are missing : Italy and Sweden, and they are maybe waiting to be revealed for industrial or modern era. Portuguese will probably be an Early Modern DLC.
Later we can expect a baltic, slavic or balkanic nation as DLC for modern, maybe ?
And there is so much important entities to get in Modern era : China, Soviets, India, one country of the Arabian Peninsula, at least one important african country (Kenya, Nigeria, Botswana, South-Africa, ...) or two, America, Australia, ... and there is a lot of potential for singular pick which never appeared in Civ.
As a Belgian : seriously modern Belgium is so boring, I don't expect them, really
Industrial era could work really well for the "industrial superpower", extreme coal mining, the trainophilia and rich architectures of this period ... But even if the industrial infrastructures continued to be used at the start of the "humankind modern era", but quickly outdated and closed a little later, and we continued to build some cool trains.(yeah it's important, railway infrastructures was ridiculously ultra dense and much too develloped for a so small country, before being dismantled and abandonned for a great part) > Still, I don't expect modern Belgian, really.
For Switzerland I don't know... their "neutral" position is a little wacky for the 4X genre ... but could be interesting : a sort of ultra defensive gameplay for a player which don't want to expand anymore and just being ultra mercantile.
But Swiss mercenaries are so important in early modern era than I cross my finger to have them as an EM mercenary corps.
Imagine : trencend Romans, become catholic and recruit Swiss Guard to make a "Papal States" run.
