It seems like you and your wife are not sold on a teardrop, I would suggest renting a teardrop (or go to a gathering) rather than spending time building a cheap teardrop so you and your wife can decide if you like it. before I started my real build I made a cheap model the size of the interior with cardboard a few cheap 1x2 boards, cut out cardboard doors etc.. That was enough for me to decide what I wanted and to convince the wife.
Also I think you are designing it wrong if you think you have to climb into it. You should be able to sit down in the door opening, swing your legs in and lay down.
As far as cheap and simple doors go check out Steve Fredericks build manual (I highly recommend buying it]) . His doors use an inside door seal/spacer for a ledge to put the door seal on. You can make them any size and shape you want. You will need a piano hinge, door handle and wood. Windows are optional or you could make Wiley windows
Check out his web site and look at his several build pictures for explaining http://www.campingclassics.com/index3.html
Good luck
Dan