It could do with the possibility to base on laps, or maybe % tyre wear/fuel consumption.
Sure, if you leave Bob to his own devices he'll come in when the tyres get ragged, but on longer tracks, he'll sometime stay out too long. Also, the tank always gets brimmed (very wasteful) unless you're in for a splash n dash when less than a full tank is required to the end of the race. If your car gets thru tyres faster than gas, this can be a big slowdown - about 60 sec per pit stop at Nurburgring 4h for instance.
Also, what's all that about when Bob tries every lap to put racing hard on when it's still wet? I had this happen in the Suzuka 1000km, which I luckily caught the end of - Bob was wasting loads of time falling off. Mind you, most of the AI cars were too so I guess it was a level playing field.
Ran Tsukuba once with the pit strength set and at the end my bobs were pitting every lap!