Marshall, If you do the "random delay and collision detection" with true 485 you will have power glitches - and maybe burnt chips - beyond your imagination. The 485 drivers are not inherently current limited and if you have one pulling down and one pulling up on the same line the current will be rather dramatic. Remember that this is a differential line, so you will have 2 drivers in overload at each end. I have seen this happen due to a software error and things got really hot. If you absolutely unconditionally and with no margin have to go multimaster, look at J1708, it is not quite as good as 485 although it uses the same drivers but at least you can touch the chips without getting burnt.

Erik