CAPPilot - Are you sure that IDs for TMCC engines can only go up to 9? Or are you talking about Multiple Unit consists (ie. making up 'Trains') with several different engines hooked up together?
The reason I say this is because I've just re-read Lionel's TMCC Booklet "The complete guide to command control" which came out around the late 1990s when TMCC was first released and on page 7 it states...
"Every Command-equipped locomotive comes factory-programmed as 'Engine #1'. You may wish to assign a new ID#, using any number from 1 through 99. To make it easy, use part of the locomotive cab number. For example, name your Lionel F3 no. 2343 '23' or '43.' We use 23 in our example."
Note: The only caveat to this is that with the subsequent release of Legacy-equipped engines the Owner's Manual that came with my CAB-1L/BASE-1L set states in part "You may wish to assign a new ID#, using any number from 1 through 98 (do not use engine 99, as this is the universal ID# that all Legacy-equipped locomotives will respond to."