I'm a MikroTik Certified TRAINER (with few "engineer" certificates, including the highest MTCINE - internetworking) and experienced network administrator (over 10 years). For 6 years I've been working for one of the biggest Polish ISPs. I have experience with large networks with many routing protocols (including many BGP sessions) using Cisco, HP/Huawei and MikroTik routers.
You can check also my presentations from the official MikroTik User Meetings:
http://tiktube.com/video/CKhm3fCqjpGpDHCHDpEqDuDsllJoKmmE=
http://tiktube.com/video/mKfm3elEjFHDIGHFLmCqpvHuplKoGnDn=
Especially - the last presentation :). I'm probably the only one that gave speech about integrating MikroTik hotspot with MySQL and Radius - and this is what you will need here, a database on a separate machine and proper login page on MikroTik, that's all. I configure MikroTik routers everyday, and hotspot is one of my specialities :).