Ground has cycles...

So why not walls , dikes and railtypes?

Cyclic railtypes would be useful for getting a slightly more realistic looking track as the sleeper pattern could be varied over say a number of block lengths rather than a single block length..

I'm considering implementing some kind of 1m block based routes and cyclic railtypes and walls would be very useful for this...

Structure.rail(0).Cycle <obj>;<obj>;<obj> - defines a railtype that cycles through the listed object in subsquent blocks.

.railtype(0,0) would be unchanged in syntax but would apply different objects in subsequent blocks respective
to how the Cycle was defined.