Nice work so far on BletchMAME!
You know one thing that would be great for BletchMAME, is a machine 'profile(s)'. - These are 'recommended' working profiles for a particular machine to work 'out of the box'.
In theory, you can get realtime feedback from MAME and have this properly integrated in the UI. Rather than currently -> if you try and setup a machine you can easily get 'an error' and MAME just closes.
For example; right now if I wanted to run a 486 setup ready to go with the latest/best MAME is able to do, simply running the .exe would give no information, help, nothing. So I would need to hunt around random forums and 'tutorials' and guess my way though setting this up. (-ramsize 16M -hard1 somefile.chd, sound ? video? what else?)
So, with BletchMAME, for example, you could easily have a simple panel that says 'IBM PC 486', its interface would tick items that you might have and or something MAME can setup, ie bios rom and floppy drive and but then easily require other user input for needing a HDD, if no image is selected it will make one. It could have all the best hardware available otherwise ready. It could also link to a mini wiki with screen grabs and instructions to get it working.
CPU - 486
RAM - 16 Meg
VIDEO - (Best video card MAME can currently do)
SOUND - (for PCM, ie Sound Blaster 16)
MIDI (for music in games to sound great, ie MT32 or something etc)
HDD (make a blank one if needed or map to one easily)
So all these things are setup and visible by the UI - from the 'profile'. - It would hilite for example if something is missing, ie if the HDD is non existent, it will use chdman to 'make one'. Perhaps later, it can have a folder mapped like dosbox does.
Also things like MIDI, it can map to what ever is best in MAME currently OR even the OS directly, ie windows midi port so I can run my own soft synth.
For floppy(s) you can map to any old disk image from the softlist and/or a real floppy on the host OS or even a 'hot' folder. But not all clunky as it is now.
Profiles could be really cool in this case; Imagine right now, if someone trying to run an AMIGA that is working or 'pretty much' in MAME but has no or little info on what MAME has or is capable of, or are not sure of what is best or even what is actually available.. they would have a classic setup that is ready to go.