The Design Process....
Welcome guys - you're in a fun place in your school careers. Senior design was a long time ago for me, but I still remember it as probably the best time I had in school.
The advice given above to define your requirements is dead on - and your response to "build a plane that appeals to the broadest market" is not refined enough. This is a learning project for you, so you're going to have to do some digging. Really define your mission. No aircraft satisfies every need - in fact, they are all optimized for something. The RV's are particularly good at doing many things well, but even they are products of compromise. That, in fact, is probably the single most important lesson you can take from a design class - the need to make choices and decide on priorities. Unless I miss my guess, your professors will be much more impressed if you carefully define your requirements, and then show how your design meets them than if you try and make something that does a little bit of everything, but nothing well.
So my advice is:
1) define your mission (Aerobatics, cross-country, VFR, IFR, all-weather, sunny weather, range expectations, etc...)
2) Dig into the Federal Aviation Regulations (part 91 is a good start) to find out what equipment is REQUIRED to be in the airplane.
3) Pick up a couple of up to date flight instruction manuals relative to the kind of flying you expect the airplane to be used for, learn what kind of equipment is used for what.
4) Iterate on your requirements with the new knowledge you have obtained - figure out WHAT you need.
5) Start looking through web sites like this one to see what specific equipment can be used to satisfy those requirements.
A large part of my job is training new engineers in the aerospace business, so I know a little bit about the challenges you have ahead. There are lots of people that will be happy to help you understand the choices you have to make, but first, you've got to do your homework. Good luck, and don't be afraid to ask some specific questions.
Paul