Okay so it's occurred to me (and I'm sure I'm not the first) that you could make a "copper clock" like so--
--with just a copper block, an observer, and whatever output you need, and have a very compact clock with randomized timing.
However, obviously this only works for 3 pulses, at which point it has to be manually reset, because there's no automated way to strip copper. You can wax it with a dispenser, but the stripping has to be done with an axe in the player's hand.
All that said... this still works for a super compact delay mechanism, say for a trap (*evil grin*) or something you only need to go off a limited number of times (or are willing to upkeep constantly...which I'm not.)
OR you could set up a piston feed tape that cycles out a lot of copper blocks, either moving them every time it updates or every time one hits maximum oxidation. You would still have to come in and manually reset the system every once in a while, and at this point I'm not sure the space required really makes it worth it (especially when you could make a randomizer from, say, a chicken and a pressure plate in less than half the time and space.)
But it's an intriguing concept and I'm genuinely curious to see if there's any practical use for something like this. The idea of a two-block randomized clock is very alluring... I'm just not bright enough to make it work in any kind of efficient fashion.