I have heard about carmelized sugar before - I think I read there is something called brewers carmel - but I really like your baking method idea!
But, here is the thing that keeps making me wonder. To have a sweet taste remaining after fermentation we need to have some of the sugar remain and not ferment (possibly) and that's why I was wondering if we mash at say 158 instead of 154 if more of them will remain and be tasteable when the beer is done.
The carmelized sugar will no doubt add to the color but won't it all be fermented and turned into alcohol thus not leaving any of the sweeter taste?
I have also read a few places that Fullers doesn't use Maize but I'm not sure I buy that at all... so many clone recipes have maize in them.
Fullers is one of these brews that has an incredibly unique taste, almost all of their products do, specifically the ESB and Porter. It makes me wonder about the brewing process more than the ingredients...
I'm probably going to make two batches soon... Mash one at 154 and one at 158 and see