It's time for decisions to be made and make them I have. I have a number of displays kicking around in the parts bin but in the end the choice was fairly obvious. The 320x240 LCD display with capacitive touch overlay is the clear winner. Along with a rotary encoder (and maybe the odd button). The display will be driven by another arduino compatible device, I'm thinking a pro mini might be a good option as this will still allow for a USB connection for debugging and control.

The LCD is a Seeed studios touch screen sheild that I purchased several years ago, at the time I ported the seeed driver to use the Adafruit GFX library, coming back to this project I found that I had not implimented rotation into the driver so this is step one, the work is mostly complete however there is still a problem with rotation of a filled rectangle that I have yet to fix (code for the library is on GitHub)

The LCD will allow for preview of waveforms etc..