I don't know if this will be of help to you but this (very rough!) video shows how my current live rig works using, like you, a very simple MIDI keyboard (no faders, buttons or rotaries) to change 'patches' set up in Reaper. Basically I use the very bottom two keys of my 88-key board to trigger actions that navigate up and down the patches, making them ready to play almost instantly
https://youtu.be/0GASrv_OjLw