As someone with a small one
(a S32) In fact I would say the small S bodied guitar might have a physical size measured in 'girl inches' but the sound is measured in 'man inches'
I echo the benefits of a these instruments. It is a very comfortable instrument to play and seems to respond and speak a bit quicker than a larger instrument of similar construction, so it's great for fingerstyle. It also strums well although it wouldn't be my first choice for Pinball Wizard.
As a plugged-in instrument, small bodies seem to amplify well, being less boomy. However, a really well made guitar of a jumbo or dreadnought guitar will outplay a smaller model of lesser quality in these regards and of course has other great qualities so I don't think there is a need to change if you already have a great guitar.
Having said that, if you want an all-round instrument that also stands up to heavy strumming, a medium jumbo might be the way to go - that's the 'A' isn't it?
Regarding pickups - you have probably seen what used to be known as a Mimesis pickup, now the Fishman Rare Earth if it was a soundhole thingy. I'm not keen on having anything like that in the way, I have managed for years with undersaddle pickups from both Fishman and EMG and I use an Award Session Matchbox DI which takes away the 'quack' from the sound. I also found the 'Shape' switch on a Trace Acoustic amp does the same and I dare say there are other good solutions out there including mixing systems that also use an internal microphone.