It's YOUR train, so you're entitled to make it your own; in this case, by adding TMCC to it. However, the modification will probably cancel-out its original value to a future buyer; except if that buyer also values the TMCC conversion. IMHO, TMCC adds much more operational fun to a loco, so it INCREASES the "fun factor" with a CAB-1 (or other Lionel controllers) in hand.
Another FORUM member already noted that TMCC-equipped (or modified) locos can also be run in CONVENTIONAL mode; use the slide switch on the TMCC Command Base to change its function from COMM (Command) to CONV (Conventional) mode and let an accompanying Lionel PowerMaster do the work - changing the track voltage (and therefore, speed) of the loco through a CAB-1.
Mike Mottler LCCA 12394
mottlerm@gmail.com