Some Great ideas here:
One or two here:
To OP. If you want "out of the box" solutions for hardware debugging, then you should move to 32 bits microcontrollers.
There are a lot of cheap options, check this TI ARM board : EK-TM4C123GXL Evaluation board | TI.com. It includes hardware debugger on-board, just using the usb (no external debugger required). Just for 13 USD.
PS: Once I tried to debug with debugWire an 8 bit AVR but the entire process to setup was long and at the end I burned my AVR debugger (Dragon).
Everybody burns a Dragon, or at least they used to although I think they are more reliable these days.
One reason I love working with LPCs is that ARMs all have debugging built in and it's supported by the IDEs out of the box.
Rob
Compare to the Due or a stripped-down compatible?
Well actually it's not the LPCs as such as I think all ARMs have similar debugging capability. It's the the dev environment that makes the difference and the LPCXpresso boards have debugging built in, no ICE required just the standard USB cable and IDE.
The Due doesn't do that. IIRC there is a debug header but you need a separate ICE for that.
Rob
Avr jtag ICE for DUE debugging is expensive (110 usd on digikey).