I figured this might happen. The sleepiness won out! LOL
The TLDR:In response to your first quote, I'm actually already using the method of attaching an SMF to a song so it plays back in sync with a recording although I specified MIDI "notes", not Bank/Patch/Program Changes. If all my SMF ever needed to send were notes but then SLM used those notes to trigger a preconfigured MIDI Preset which handled the Bank/Patch/Program Changes it would be the perfect combination.
The Details:I think the goal is more of a workflow/productivity thing. Some DAWs, mine included, make working with Bank/Patch/Program Changes in a visual way, very difficult. As a matter of fact, some don't really allow it at all and you're relegated to using an event list only. To be honest, it's not much different than how I would edit an automation track in SLM.

I currently use my DAW to create an SMF that handles all preset switching for an AX8, GT-1000, custom pedalboard, VoiceLive as well as lights. They all have their own MIDI tracks and channels and the time it takes to enter the Program Change events in the Event List and adjust them as needed backward or forward to account for Program Change latency and such is crazy and super tedious. And this is for every song!
So it got me thinking...on one hand, in a DAW's piano roll view, dealing with MIDI
notes (instead of Bank/Patch/Program Changes) is a piece of cake, right? Click the grid, there it is. Need to slide it forward or back? Drag it and done. Not to mention that, at least in my case, I'm doing this against the audio backing track (on it's own audio track) and am hooked up to the device I'm currently working on via MIDI so I can see and hear the changes in real time.
On the other hand you've made the job of managing MIDI PC changes very easy and compartmentalized with the MIDI Presets functionality. So if I could combine the best of both worlds I could be far more productive. If a MIDI note on a specific channel in an attached SMF could internally trigger MIDI Presets as/when needed throughout playback it would be amazing.
I understand that my workflow is not the next person's but maybe it's useful for more than just me? The thing that could nullify the need for this request would be a timeline-based editor that would allow for placement of Recordings, SMFs, MIDI Presets, Lyric lines, etc. I also understand the potential complexities of that as well and now you're dipping in the DAW area. Steinberg seems to be trying to address this world with their new app but it still requires a Mac or PC.
I hope this helps but please let me know if you'd like clarification on anything else!
As always, thank you for being so responsive whether we are looking for help, making suggestions, etc.! It really does set you apart from other app authors.
Mike