This is an area where HO has a real advantage over O, because the digital control system used in HO is NOT proprietary to the loco manufacturer and is not necessarily built into it mechanically, thanks to the use of an NMRA “plug & play” connector used in many locos from different manufacturers. Of course, there are no optical tachometers either, to further complicate things and add to cost (and HO seems to get by pretty well without them). If you don’t like the system in your loco, you can change it!
Bill in FtL