The format needed to be able to support all memory types for all supported consoles, so the 1-letter identifiers weren't really good enough anymore, this was the simplest solution code-wise. 2.0 was never intended to be backward compatible - save states or movies aren't either.
There is no way to import/export breakpoints - though you can extract them fairly easily from the workspace json/xml if you need to.
Not sure what you mean by dylib exactly? Or did you just mean the .so? Using -g -O0 as flags should work fine as far as GDB debugging goes, I've done this a few times. I'm fairly sure I've run it through ASan at some point, too, but it's been a while. If it doesn't add too much complexity to the makefile to add these as options, sure.
Speaking of dylibs, currently in the process of fixing a couple of things for macos, but it mostly works atm, so hey, maybe the macOS port people have been asking for ~6 years will be a thing at last. :p
I'm almost sure I've had this exact discussion with someone before, but I can't find a trace of it on my future ideas list. I'll add it to it and see what can be done eventually. The attribute data byte is easy to add, so I'll add this soon since people seem to think it's useful.
1/2/3 should all be pretty easy. I'd like to avoid 4, since it'd be a NES-specific tool, and probably not something that would be used very often, in most scenarios. Editing through the memory viewer should be good enough when the need is there.
Thanks for the report! I think they actually do work, but the PC Engine core's resolution is ~1024x717, so if you turn on 2x xBRZ, it produces a ~2000x1400 picture and then shrinks it down to a lower resolution depending on your window's size, which makes it really hard to notice any difference. This is a bit tricky to fix since the 1024px wide res is needed to be able to display all 3 of the pce's "native" resolutions properly. I'll try to see if I can make the resolution auto-adjust based on what the game is trying to display, which should make the filters work better.