Having finally bought decent flight controls with more switches and buttons than I know what to do with (VKB Gladiator and STECS Max) it looks like I’m in the market for one of these apps.
Do either of them let me configure a base set of bindings for all planes and then overlay modifications for individual planes? Or some kind of template system with inheritance?
I really don’t want something where I have to copy-paste-modify for each plane as that rapidly gets out of hand.
Can’t speak for AAO but Spad currently doesn’t. You can create a new profile from an old one, but you can’t do profile inheritance. It is on the list for a future version but no timeline has been given AFAIK.
I have a base profile which has just the common mappings I will use in all aircraft (eg a full set of mappings for my G1000 hardware) and then I create a profile from that and add/alter as needed. I also wrote a small tool that will copy an entire device’s mappings from one profile to another, which I have to use if I expand my base profile to avoid having to change every profile one by one.
Since Spad profiles are XML documents, if you’re handy with a text editor you can actually do a lot of work outside the Spad UI, which is good for bulk changes.
Ah xml makes it pretty easy. And there’s not much I can’t do with Emacs. 
Except having a very sore pinky?
Spad has probably all you want, is very advanced handling hardware. You can store XML snippets for each of your peripherals and configuration you want. Then you re-use the snippets you like a voila! you have a profile for the plane.
This can also be done in Spad without dealing with XML, you can for example create a profile based on some default one or generic one and then import for each peripheral a configuration from any other profile.
I was thinking the exact same thing. Snippets are a great start. I’m still learning to use variables, and the one downside (AFAIK) is that, while a snippet of code can refer to user variables, they aren’t saved with the snippet. That’s where XML editing might come in handy.
I’m talking above my pay grade, so I could be completely wrong about that. In fact, I hope I am!