Just keep reminding yourself, that the pain and agony you go through now,
will be well worth it when you have the end results totally to your desires!
Cabinetry ... there are some door styles with ridges going the length, rather than the picture frame style with lots of dirt catching nooks and crannies! Perhaps that would be a good meet in the middle style for the two of you? Drop by some other kitchen places, even ones you don't expect to be dealing with, and put the question to them, and see what they suggest. Also, your kitchen designer should be able to help with suggestions. It won't be the first time they have had this requirement laid out for them, I am sure!
Garbage ... don't forget to plan for recycle, compost and how many other "sorts" there are to garbage in your municipality. When I re-did my kitchen at my old house, I created a drawer with three bins in it .... garbage, recycle and paper. I liked it so much, that when I moved to my current home, I converted a kitchen cupboard into a pull out drawer with the three bins. Works fine for me. Unfortunately, my only option for compost at this time is an old covered juice pitcher that sits in the corner of the 2nd sink. It works .... but I would prefer to have it hidden more so.
One friend put a hole in her kitchen counter to be able to drop garbage into the trash bin, sitting on a pull out. Good idea, but IMHO I hated it ... a cleaning nightmare, as you had that hole to clean as well as stuff that seemed to miss the garbage can below.
Putting your garbage separate from your cabinetry is an option as you have suggested. Many kitchens, there just is not the space to do that though. With a re-design, maybe you can make it work. Or perhaps a whole garbage centre built into or against the end of the cupboards.
One thing to think about in separating the garbage location ... convenience!
To me, I would sooner have it right where I am working, and creating the most garbage and not having to take it to a bin. Less movement, means less dropping of stuff between creation and disposal .... and less clean up for me!
I'm envious of you and your new kitchen. I want one so badly, but it is not in the cards for now.
Have fun planning ... taking your time now will mean no regrets after the fact!
Good Luck!