Very true. I always like to have a command that makes sense used as a flank-march, especially with an infantry-based army like the Visigoths (get in behind the oppo., so that he can't run away if you start to win!)
Personally, I'd go with the ally-command if you like the options it gives and live with the fact that 1 in 6 times it'll be unreliable! That's why you pay less for AGs. When you don't FM with him, stick the command somewhere where it'll be useful even if unreliable:-
1. Up front and in the middle is good for making it very difficult for the enemy to avoid approaching it and thereby activating the unreliable troops.
2. Holding a refused flank is also handy, as it can be difficult to get around them without, again, activating them. The advantage of Reg Cv(S) is that they'll manoeuvre backwards at 1 PIP a time, so you can deploy forward in the hope of being reliable but can back-peddle to counter enemy that try to get behind them if they turn out unhappy (remember that you can still move if unreliable, as long as you don't get closer than 800p to enemy)
I speak as an inveterate SRB-user, with 2-3 compulsory AGs (albeit usually internal ones).
Tim Child