If one used the Visual Roll Reader (a.k.a. VRR) to make an Ampico MIDI
file I don't think tempo changes would be an issue because the VRR
analyzes the roll as it goes over the tracking bar on the actual piano.

You can get more information of the VRR at UniversalMidiController.com

Full disclosure: I wrote the VRR and run the web site at
https://www.universalmidicontroller.com/ 

Dave Burritt - Vintage Slots of Colorado