Yes, if I would (if I had the time) do the following
Make a alias for the POSIX CLOCK_REALTIME -> CLOCK_UTC. Make a new CLOCK_TAI running along CLOCK_UTC. And some function to get the difference between CLOCK_TAC and CLOCK_UTC at any given time (except you don't know about future leap seconds).
Many POSIX API implicitly CLOCK_REALTIME=CLOCK_UTC. Alternativ APIs must be made where the user can choose between CLOCK_UTC, CLOCK_TAI, CLOCK_MONOTONIC etc. In many (most) cases CLOCK_MONOTONIC would make most sense.
In the applications I am working on right now, I would try to restrict myself to CLOCK_MONOTONIC and CLOCK_TAC, but I would need to translate to and from UTC because some protocols require timestamps in UTC.
Right now we are using CLOCK_REALTIME and using arithmetic on the resulting struct timestamp to find time differences.