Jobi,
Sorry, no experience in this area. Clients I have had the pleasure of serving elected to avoid the issues that would be raised by embarking on such custom development 
.
Make sure you get a complete list of all possible availability scenarios while gathering your requirements for this solution. Otherwise, client acceptance testing of such a solution could end up being.....challenging....for the consulting team.
Hope you can keep us in the loop of how this project progresses. I for one will be curious.....
Good Luck & Best Regards,
DB49