I like B-Spec as it is (for the most part). The only thing I'd like added is an x2 time compression. The races are longer anyway, so I think this could be done without throwing it out of balance. When you first start, it's very frustrating and you definitely have to babysit them through a large portion of the race. But after that, it's not too bad at all.
Once you've got one driver up to lvl 15+, advancing the rest of the drivers becomes much easier - you can basically throw them in the deep end using superior cars and use the knowledge/experience gained from leveling the first driver. With the right combination of car (easy to handle) and track (lots of straights, few technical corners), a new driver can easily win races 5-6 levels above his current level.
Some of the prize cars you get are fantastic as well, and can be invaluable in A-Spec.
Once you're confident of B-Spec Bob's driving ability and you're familiar with the GT5 menu system, you don't even have to switch to the PS3 to assign commands. If I'm watching a movie, for example, or doing something on my computer, I'll have the DS3 controller close by (this is when bluetooth is fantastic, no line of sight needed). If I already know the cursor is pointing at the issue command icon, I just press X on the controller a couple of times, and I know it'll issue the last command to the driver. If your driver typically slows down once his temperament cools down, I'll just mindlessly hit the X button twice every 50-60 seconds without even thinking about it to issue a pace increase.