I've been reading a lot of the recent posts and I think the most important thing that the developers will need to decide on for DMC5's combat is whether or not they should get rid of the style system. I personally think they should and instead make all your weapons (assuming Dante will have 4 or 5 devil arms) go on the D-pad. The triggers could then be used for variables.
The Right Trigger could be the dedicated "gun modifier" button. Pressing it by itself wouldn't do anything, but holding it down would change the function of your shoot button, allowing you to use Gunslinger style moves with the X button (or whatever you use for the shoot button). You would also be able to switch guns by holding down the Right Trigger and pressing directions on the D-pad (again, assuming Dante would only have 4 or 5 guns).
I think DmC was also onto something with the dodge button. Mapping the dodge button to both LB and RB was a stupid decision, but maybe having one dodge button on the L or R bumper could work as your Trickster style button?
This would make the placement of the Devil Trigger button questionable, though. I dunno, do you guys prefer having Lock-On being on one of the bumpers, or on one of the Triggers? I think both could work, but if Lock-On was kept to the bumper, than Devil Trigger would maybe have to be on the Left Trigger... That could maybe be used as an excuse to expand the use of the Devil Trigger, though. Maybe, during Devil Trigger you could hold down the DT button and press one of the face buttons to do a special DT-only move that consumes the rest of the DT meter? It could be used as one last attack/movement option before it's used up (or maybe holding down the DT trigger and pressing X would give you Doppleganger and pressing Y would give you Quicksilver?)
I think having B being used as another Sword button would make sense... it'd essentially be the dedicated Swordmaster button. Dante has enough moves for most of his Devil Arms that two buttons for it would be needed.
So, instead of completely getting rid of all the moves the Style System gave us in the past, maybe they could just be given their own dedicated buttons. Choosing weapons with the D-pad would be so much easier and would be vital if Dante were to have more than 2 or 3 weapons at a time(which I think is a must going forward).
I don't think this would be "simplifying" the controls so much as simply updating them so that players could not only have easier access to Dante's arsenal, but also so that Dante could have more moves at a time than ever before.