Hello there,
I have just seen your project and i think i am quite qualified for making / modifying your fiverrscript..
I have expirience with fiverr as you can see here [login to view URL]
And i really have sales there :) on fiverr :) So i kinda tested all of it.
I dont actually think you need team of web developers for this, mostly because stuff you mentioned you need are not so complicated, and also important is that single man code is always easier to modify and upgrade, and kinda works better (ask any web developer with 7+ years of expirience).
I`ve tested fiverrscript, and i think it is okay, though i find that it has some security issues and it is not protected so much (the way most people probably think it is)... so i would tweak security a bit too.
You mentioned front end, and I just have to say, we can modify / design anything, really anything you want - so there would be no problem with that. Also you said file upload for each user and I can develop that easily for you too in whatever technology you would want me to ajax / php / python / whatever...
I think i am right person for this job, mostly because of your last sentence - long term relationship. I am new here on freelancer (i had an office and well, everyday clients, which are still my clients) so i am really looking for long term relationship as I am used to do that.
Wish you a grate day,
Hope you are interested :)
Honestly and with respect,
Stefan