Ok, I may be living in the past, but a "scaly system" to me does not by necessity mean that the "Power Base" is the world standard unit to be expected in a Scalextric layout, especially as it wasn't even mentioned in the original post! I might be wrong in the respect of contemporarity, and if so I'm honestly sorry I didn't mention this gadget in my previous post. But astro is absolutely right about the rectifier in the power base unit and the problem my suggestion in that case would have caused. Thanks astro for the heads up!
Several suggestions have already been made since my post in this thread now, but I still have a few sents to add: If you want to solve the issues you have skeeter: get rid of the power bases once and for all! And if you read between the lines of the other posterers ideas, this is what they ultimately suggests! Correct me if I'm wrong here guys. But I can not see any advantage of using this silly "Power Base"-system except for the fact that the novice could hook the track up with a little bit more ease than before this Great invention! And I managed to connect my Scalextric track at the age of four in the sixties without any Power Bases...
If you fancy a master direction switch in a 4-lane layout, get a sufficient single DC transformer instead of messing with a bunch of AC (or DC for that matter)-units per lane. The problem of having a 4-lane layout using power bases in opposite direction just vanishes the very same second! And if you do go for that, it's still very simple to add direction switches for each lane if that is the way you want to go.
If you would ever come to the situation of using controller with diodes (so called electronically controllers, which is by the way overkill in terms of cost in amateur business), this will never be a problem as long as you deal with switching the polarity to the track rails rather than to the whole system (before controllers), wich in fact is a cup of peanuts to wire up if you have the slightest skill in reading wireing.
If not, I suggest you ask your buddy to do the soldering. These things are not high tech stuff, just pure simple routing. There is a lot to find about this on the net if you just spend some time on it.
Still wish you good luck!