I've been working on this mount which bolts into all 4 of the factory holes just like the stock bracket but fits a 6.5" speaker. It's perfectly centered from where the stock 5.25" speaker was and just about the same height as well. All without doing any cutting to the door. Unfortunately with the poorly designed door panel it'll need to be cut so I'll be reworking this to come up with a solution. If anyone cares to share what they've done to fit a 6.5" I would appreciate some references to work with.
Here's what I have as a first prototype: