Thank you for your posts!
I think there is some confusion about the idea, I will try to explain. First of all the PTO system will not be placed on the quad because it will most probably ruin the balance. It will probably be pulled behind the quad on wheels with a separate engine and possibly a hydraulic pump which can be connected to existing (second hand possibly) mini hay balers, mowers etc. So in case you already have a quad, it will never be as expensive as buying a tractor with equipment. The PTO system will be the only product I will be designing, so I will not design a multi task quad or a full range of equipment (the existing equipment should fit on it). My target group is hobby- and horse farmers.
@Robert; I am aware that I am the student and I will not claim any accolade for these ideas, these forum post will be in my report in the appendix. I am nowhere near a professional farmer though, so I don't know the best of farming and the machines. I have to get ideas and information from somewhere though, why not ask the professionals?