First:
A somewhat unrelated question: My remaining 2 switches control OD and Delay status globally ~ is there a way to assign them per preset for more functionality?
Yes! Set them up as external controller switches and then assign them freely, per patch, to functions. As external controller IAs they can be assigned to more than one thing (even more than one thing at a time).
Now back to your larger problem. There are many ways to, ahem, skin this cat so to speak. Yek mentioned one. I'll lay out a few options as they occurred to me while I was thinking about your request.
Option #1: Keep your patch setup, exploit bank limits and wrapping on the MFC to make it easy to change EG -> AG and back with one button
I already talked about limiting the banks on the MFC and I had an expansion on that thought that you may wish to consider. Let's assume that you have your 15 EG and AG patches set up so that P1 = EG and P16 = AG for the same song. That is, you have things organized in two patch "pairs", spaced 15 patches apart.
If you're playing a song on EG P2 and you need to switch to AG mid-song you'd be switching to AG P17.
Following?
With this organization, you can setup the MFC to move from the EG to the AG to the EG to the AG patch for any pair with one button press. On the MFC you're going to set:
- Bank Size -> 15
- Bank Style -> CURRENT
- Bank/Song Limit -> 002
- Bank/Song Wrap -> ON (this is different than what I said earlier)
With this setup, the BANK UP and DOWN buttons both do the same thing: they take you from the current patch to the corresponding AG or EG patch. If you're on the EG patch and you press
either BANK UP or DOWN you end up on the paired AG patch. If you're on the AG patch and you press
either BANK UP OR DOWN you end up on the corresponding EG patch.
This approach has the advantage of allowing you to use the full power of the unit for AG and EG patches, no compromises. It also lets you quick-hit one switch, BANK DOWN, to do all EG -> AG -> EG -> AG toggling. The disadvantages are in the limits to the patches you can use (17 tops, but 15 if you want to keep two switches as IA switches without going to external switches for IAs). And because these are patch changes there can be a very short delay on change (but you said that's not a problem for you, so that's cool).
Option #2: Switch your setup to scenes
This is the more involved option. You're going to have to re-work your patches. You've already stated that you're pushing the CPU limits of your AG and EG patches so your best approach is using the X/Y states of your blocks and, where blocks differ for AG and EG signal changes, switch the X/Y state on scene change.
This approach requires you dedicate an IA on the MFC to selecting the scene in the patch. Scene 1 will always be your EG scene, scene 2 will always be your acoustic scene. You can use the mixer block and scene controllers to route the signals in the scenes when you need a slightly different signal path. Here's an example.
Scene 1: Electric Guitar
The signal from the front input is routed through some pre effects, the AMP + CAB block and then on to some post effects. The signal from the rear input is muted.
Scene 2: Acoustic Guitar
The signal from the front input is muted. The signal from the rear input is routed though some of the same blocks, but those blocks have been flipped to their Y state and use alternate settings. Then there's a slightly different post effect signal chain that's selected by the MIX block having it's mixer settings flipped by the scene controller assigned to the values.
Edit: have to go watch the kids for a while. When I get a second I'll post an example patch for you that shows what I'm talking about with scenes and routing.
There are more ways than these two to go about accomplishing what you want to do, but these two feel like the most viable to me right now.