The Bolide might be the perfect compromise. I knew nothing about Bolides until I joined this forum. All I knew about were Birkins and Kellys. I now own a Kelly and thanks purely to HiHeels enthusiastic thread, the most beautiful Bolide. I don't have a Birkin yet but I'm hoping...
I can only compare my 35cm Kelly and my 31cm Bolide. On the whole, I find the Bolide more practical. The zip means that it is so easy to get in and out while it is perched on your shoulder, unlike my Kelly which is a little more 'clumsy'. Also, when the Boide is unzipped, it retains it shape and appears closed unlike my Kelly which dangles open, so I feel a bit less prey to pickpockets with my Bolide and also, it just looks neater, open, than the Kelly. The zip goes a long way round so it is easy to get at everything in your bag. It can be operated one-handedly; I usually need 2 hands for Kelly. Also, overall, it is quicker, in and out, compared to Kelly. If you like the shape of the Birkin, then the Bolide has the 2 handles, the cloche and padlock, it's just the streamlined curve that makes it unique. I also have a Massai which is very comfortable and practical but I do find the access can be a little more difficult compared to my Bolide, the double zips are more awkward and can catch your hand and there is less room and access into the bag compared to a Bolide. My Bolide is stiff leather in 31cm but I love it so much, I am considering getting a mou version in 37cm as a travel bag, that will have to wait until after my Birkin...