A great starting point would be to add just about all the functionality that PSI version 2 had. Sure that program could be improved, but to me, it always seemed surprisingly close to perfection. And as I have been unable to find an alternative program that really fits my preferences (PSI version 3 never really seemed to leave it's beta stage), I'm really exited about the PSI alternative you are working on. I'll definitely be following this project with excitement!