Keep it stupid, stupid
Not sure why Ford would ever spend the resources on developing a new I6 when there is a perfectly good 2.7/3.5 that works well for the Mustang.Mustangs already compete with European sports cars as is. The Mustang never competed with the little go-kart cars like the Miata or BRZ. Very few mustangs were actually "good handling" cars. SN95s, and newer are about as good as your going to get in a Mustang when it comes to handling except maybe a 65-66GT350. As a car that currently rates 2nd place in the 3-way muscle car wars, with the Camaro about to die again, the Mustang will still take the crown even as it sits weight wise and center of gravity wise. Also the Barra 325-T 4.0L inline six fits perfectly under the production hood of a GT350 so it wouldn't be an issue. An I-6TT fits under the sloping hood of an M4 or M3 so it would work fine in the Mustang and the Mustang originally came with an I-6 from the factory in the 60's so it would still be fine within the specs of "Mustang" And your thoughts of an AWD system throwing off the center of gravity makes no sense when nearly every Audi performance vehicle has an AWD system, so do alot of Porsches, every new GTR from 2008+ and now the M3/M4 and alot of them will hand a mustang a healthy beating in just about every single scenario all without a v8. Don't get me wrong I love the sound of a V8 engine and the feel of one as well but Ford needs to get with the times. Sure a small 4.0L v8 twin turbo or 4.0L twin turbo Hybrid V8 would be awesome under the hood of a mustang with an AWD system in several different body types. But if the Mustang is to survive, it needs to not be pigeon holed because if it does, it will die out just like the Camaro. Having a mustang family would allow the vehicle, and the name, to live on.
I do think that the Mustang will be offered with AWD, but only in a hybrid engine configuration. I also see the 5.0 soldiering on as the same 480hp motor from the Bullit/Mach 1 but with very little development happening throughout that generation until it finally disappears for the S750.