There are lots of possible answers, none of them especially useful
- go manage somewhere that has different work permit rules
- pick players who will qualify for a UK work permit (suitable % of senior international appearances or a young player of great promise)
- if you're big enough, have an affiliated club in a country where citizenship can be obtained quickly, loan them there, bring them back
it's really irritating that your competitor clubs will probably be able to get work permits for players you cannot. how this is fair I don't know. perhaps those clubs are practicing "greasing the wheels" (aka bribery).
one joy of managing a German side is there are very few restrictions.... in the domestic cup, you can't field more than three non-EU players on the pitch, but for league and outside competitions there's not even that limit, and no roster limit.
well, this stuff is not invented by FM anyway!!!! (although I'm not sure they always apply the rules accurately enough)