As usual, QF, you and I are on the same page!
I use my Evie this way as well -- the outside pocket kind of sealed the deal for me when I bought mine.
I think your instincts on the Jypsiere are right. If the flap and straps on the Kelly drive you nuts, it's probably going to be the same for the Jypsy. Re. the Birkin, the lack of a shoulder strap is a deal-killer for me on this bag. I'd rather deal with the Kelly turnlock and have a strap than have an open bag with no strap. It all depends on what works for you.
I like the suggestion others made to get the Evelyne now and maybe get another Kelly later. If/when you do get the Kelly, try a 32 retourne -- that may make all the difference in the world.