I wish the whole feature would go away. It can't possibly work correctly anyhow:
Control is given in a random order during diplomacy. Thus, one never really knows whether one will control it at the right level of control when needed.
Russia and GB (me) used this tactic at the beginning of the game: Russia DOWed Sweden after I had gained influence, and I DOWed Denmark after he had gained influence. Gamey, yes, and I'll cover that later.
Anyhow, for the tactic to work, we had to KNOW that we would have influence and NOT ally at the time the DOW took place. But, it's pure luck whether or not you get it, because you can't know what other people did until the end of the phase. (This is an example of "dumbing down the game" for PBEM purposes, by the way.)
Anyhow, it's just not reliable.
Anyhow, regarding the "gamey" tactics that can be used: A very simple game change should be implemented to prevent these: You can't declare war on a minor that one of your allies has influence on without breaking the alliance. This is already in place for ally status minors. Extending it to influence makes sense.
Again, though, because you don't know if you can or not, there should be a check box to not DOW if an ally gets influence before your own turn in the diplo order. Either that, or such a prohibition only occurs for values at the beginning of diplomacy.
At LAST! The greatest campaign board game of all time is finally available for the PC. Can my old heart stand the strain?