Customisation ??

Hello,
I really like your plugin. As i manage a pet hotel, the plugin doesn’t fits some of my needs… The main need is i disallow arrival/departure on wednesday – but client can book from day before to day after (you can check in on tuesday 1st and check out on thursday 3th). Also, the hour arrival field would be modified and an departure field added, both requiered – in my case from 9.30 to 13.20 or from 15.30 to 18.20 – Do you think it is possible (with additional fees)
Thanks