Personally, I don't find making adjustments very easy...with maybe one notable exception... Tobin's plate. His plate inserts make webbing adjustments relatively painless. You still have to futz with the left waist D-ring, waist buckle and maybe the crotch strap, but the webbing adjustments on the plate are much easier than with standard plates where you have to play with keepers. Either way, marking the webbing helps a lot...much better than guessing each time or going by the indentations left in the webbing from a previous use.
I prefer to have a different plate for each setup. This gives you a couple of things. You don't have to make webbing adjustments and you have plates of different weights appropriate for different exposure suits. For instance, an Al plate might be just right for a 3 mil, but a standard SS plate might be better for the 7...and an even heavier plate might be best for a drysuit. While this might not be an innexpensive solution, it does make use of the unique advantage of interchangabilty that a BP/wing offers...fine tuning for different needs.
I'll admit, however, that there are times that I use a plate that has been set up for a 1/4 in suit with a thin shorty. It's a little sloppy but not too bad.