And that's "absolutely trivial"?
My understanding of delay lines is that they tend to add a fair amount of "fuzziness" to the signal going through. If the signal is only being delayed by a few hundred nanoseconds, it can remain reasonably clear, but delaying a signal for tens of microseconds while retaining 100ns accuity would seem difficult. I know storage tubes could almost certainly do it, but those would seem to be overkill in a consumer-grade television set.
The only thing I can really imagine could have been done differently with a color standard while remaining easy to decode would have been to do something like what VHS does, amplitude-modulating R-Y and B-Y at different carrier frequencies. This would have had some advantages, I guess, but I think bandwidth issues would be a problem.
Being silly of course. There would be a snake of line, but in big tube type sets it wouldn't have any trouble fitting somewhere in the cabinet.
Another way with no delay line would be to present blue, green, red in sequence and the tube would scan them each in succession before ratcheting down to the next line. It would require a stairstep function generator for the vertical scan but that is doable with tubes. The corresponding monochrome would do the same except of course with only one gun.