I think if you're going for an aesthetic representation of how the 'in-world' people would make their maps, then using the appropriate ConLang on the map is very fitting. I've always found it interesting how maps in real life often reflect the biases/perceptions of whoever designed them to some degree, so this sounds pretty cool to me.
Though I do think that the further you go into ConLang territory, the riskier it is - i.e.: if the spellings are too unusual/difficult to pronounce or you've written everything in a constructed writing system, but with only four countries and not a huge amount of small detail, it's probably fine regardless. (anyone who doesn't want to delve into figuring out ConLangs won't feel like they're missing large pieces of key information etc.)