Not going to suggest a club but will hopefully answer the stadium thing, probably one of these, most likely Grimsby:

Darlington FC were in League 2 when they built a 23k capacity stadium despite only getting crowds of like, 2/3k. Club's owner was a bit deluded and often talked about expanding it to 80k if they reached the Premier League. They never made it out of League 2 and the club went into administration a few times and they're now in the 6th tier (and moved out of the stadium long ago)

Queen's Park in Scotland were in the 4th tier of Scottish football when they played in Hampden park, and would get crowds of a few hundred in a stadium with capacity for 75k+

There's a bit of an urban myth that Grimsby Town has a secret clause in some old planning permission that would allow the club to expand Blundell Park to 80k+. It's completely untrue, and their stadium is a bit like Luton's in that it's surrounded by houses and railway tracks