Lol. That's very true, it is quite fun. But yeah, you have a point about the rein restriction, it bothers me now and again as well. Bumping up the bit isn't really an option for him though because he is BEYOND picky. He is naturally quite the head tosser, and although he's gotten so much better than he used to be (with and intermediate/advanced riding it's virtually non-existent), if you put anything in his mouth other than a D-ring french link, the tossing ensues. So my options with him are either handle him without the martingale and risk forgetting the course (I have a hard time with it as it is xD) or using it and deal with the rein restrictions.
ETA: There's only a certain extent to which a martingale can be unnoticeable to a horse. You should be able to use an opening rein with it, but there will always be some interference. It depends on how sensitive the horse is.