I checked with my dealer today and he contacted tech support for the info. Present units with the 805xxxx or later serials can be returned to the factory for the function to be enabled. It MUST also have the full key pad to work. I had a 3180 serial 9xxxxxx so it is on the way back for the retrofit. The 2180 was a 7xxxxxx serial, AND no full key pad, so two strikes right there. I decided to just go ahead and order a new one with the feature installed.
This upgrade is apparently independent of the firmware and programming software updates that allow the MDC-1200 usage, because that worked fine. Trying to enable the Tactical Feature set, though, yielded a message that said the feature was not "activated" on the radio.
I have a Motorola HT-1550XLS for VHF and was considering getting one for UHF although I prefer the Kenwoods. This made the decision MUCH easier. Of course, the fact that Motorola quit taking orders for new HT-1550s the day before yesterday, thus starting a 5-year end-of-support period, made the decision even easier.
Oddly, the two mobiles I have are the 7160 and 8160 which always have had the field programmability option in them!