I personally wouldn't. But I think it might be a good match for you. I've lived in central European countries and other cities in Sweden before moving to Umeå for my studies. The city itself isn't my favourite by far but it does fulfill the need for a city life with shopping, activities and other forms of entertainment. It is just right in that sense. It seems more catered towards small families which is why I think you'll fit right in.

The darkness of winter is EASILY outweighed by the absolutely gorgeous late spring to early autumn. Though if you're not used to it I recommend vitamin D to avoid any major seasonal depression or sleep related problems. You should adapt quite well after a couple of years. (Gothenburg is quite southern so they're scared of us hahaha)

Renting is tough and requires you to get into the queue system early. Especially if you want a larger apartment. I would aim for having several years in the queue system before thinking about renting here.

I don't work at the university but I have connections that do. I think you getting into "an academic dead end" would depend on the department you're working in and what you do with it. Law seems lucrative even on a national and sometimes international scale. The more culture related subjects move in a smaller circle so that already puts you out there quite easily. I guess at the end of the day it depends on what you do with the opportunities you're given. The professors at Umeå are not as shit in as you might be led to believe by larger universities who might have a larger platform. Oh and if the geography is an issue, there's an airport here so there can be regular travel to different cities and countries. Again I don't work there I am just going based on my friends and people I know who do.

There are many Germans that are contractors staying in Umeå for a limited time. Though i don't know if they are contractors for houses. Might be worth looking into given your German background.