In fairness if you gave me a list of Elche, Levante, Cadiz, Celta, Mallorca, Espanyol and Eibar... I wouldn't be able to tell you who were still in la liga and who had been relegated in the last few years.
The small sides in Spain are very small. I don't think a promotion should give you that huge of a rep bonus in Spain. Most that come up go back down straight away (and often down again), I think a rep bonus should be more significant after becoming established or top half. I think it should depend on the league.
In terms of budgets... Oviedo don't boast incredible attendances. The TV money in La Liga is nowhere near what it used to be. Therefore promotions aren't worth as much as they are and it's sensible for a board to restrict and hope and be fiscally responsible.
Of course clubs are going to want money for their players, especially if they know you now have more. That's called having a good, competitive AI. Surely it adds to the challenge and realism, no?
One of the worst (but also beneficial for the human manager) in the last few additions was the stupidity of the AI allowing you to loan the same player for 3-4 seasons and demanding no money for him. I can see where it could happen IRL, for example, if in season 1 you loaned the player and season 2 you got promoted and therefore he had a chance to play at a higher level and get more valuable experience. But thankfully the days of being able to abuse this for seasons on end seem to be gone.