I really liked the idea about having the groomsmen walk down the aisle and then sit in the front row or even perhaps in their own row. Allow them to contribute to everything else but does symmetry really matter that much.
Your fiance is allowed to want his buddies to be in his wedding, and if he wants that and you are ok with it then go for it...but don't vill the void on the other side with random women that you barely know. People will forever ask you in your pictures....oh who is your bridesmaid, who was your maid of honor etc.
Anyways I have a really similar situation and don't really have that many close friends. My FI and I have been together for almost 5 years in sept and we have a 3 1/2 year old Daughter who will be a part of the ceremony as the flower girl. Being a mom and a bit of homebody sometimes means that the people I am close with seem to be the ones I work with, and I hear what you are saying about it feeling awkward. I do have one friend from school that I still keep in touch with but I don't know for sure if she is going to be able to make it. I haven't decided yet if I am going to have a bridesmaid or maid of honor yet....and I guess I will have to see in a little while and get a feel for what the ceremony will be like.....on the other hand I am having a relatively small wedding with probably 20 people coming from another country to cruise with us and so I was thinking really any girl friend that does come (and I think there might be two) could just stand with me and I was thinking about having a more casual bridesmaid - bride relationship....just show up, wear dress, have a fun vacation!
Sorry went on a tangent there a bit.....anyways I think that you will find the right balance for you guys. He is set on the guys so the guys should stand on both of your sides....do you have a guy that is special in your life...a closer friend than a girl? that might be an option as well.
Good luck and whatever happens just make sure that you are happy and then it will be all good!