Well said Colbysound and Chet. I agree with the master fader and phantom power, and I'd also like the "third" channel to be a normal channel like the other two and not just an AUX plug in.
And while it's not an S1 Pro "feature" per say, I'd like to see access from the outside of the backpack (like an X shaped slit) where you can plug in the charge cord without having to remove the unit from the bag. It would make it easier for a quick charge-up between gigs.
I'm also with Chet and ColbySound. If you can find yourself on the internet a Line6 acoustic Variax you'll wave goodbye to all your troubles. It used to suffer from the sound cutting out for no reason but if you internally run an insulated 'earth' or negative wire and connect all the 'earths' (control board, bridge, main printed circuit board) points back to the earth on the jack you will cure the problem. So you should find them for a good price on the internet. It is by far the most comfortable and versatile guitar you will own. I'm not a guitar collector any more!! yeeeaaaah!!!!!! (as Kermit would scream).
New discussion for this comment. Please see: S1 Pro request for update to allow you to connect a subwoofer to line out
For me are:
1.- Bluetooth and/or Wi-Fi to control the features on the S1 from a tablet or smartphone that would have an open source mixer with a master volume (remember Apple is not open source please). I think this should be available across all live music products anyway. Wireless speed here is not needed. Its fast enough as it is for this purpose.
2.- No tone control. I don't believe tone control has a place on a power amp. That Tone-match engine, yes. But no conventional tone fiddling. Acoustic guitars have a preamp onboard and musician with electric guitars have their pedals. Other instrument don't need preamps. Tone control is a waste of time and effort. My Bose wave radio doesn't have it nor my L1 compact.
3.- UHF out for in-ear monitoring (I'm pretty sure its UHF). Just make it available for already available receivers out there. There are plenty of them. Internally, hook it up to the existing line out. Volume is already available on the receivers. Just raw UHF signal out. Functionality for 3, maybe 4 receivers.
None of the above would affect the sound technology that Bose has been using since the 60s and getting money for old rope.