I had thought of that as well, but for my specific purpose currently I need a hotel booking system. I may revisit it later and change it to a general reservation system. The problem with focusing on that now is that A) I don't have time to implement all of the requisite functionality and B) it would require being able to establish different time periods rather than a full day -- which brings us back to issue A.

Some of that functionality already exists with events, and the other things can be accomplished with regular products/product classes. I am doing ticket sales on this same site, and am using product classes for the various ticket types. Each date will have its own ticket product assigned, because pricing varies more. While it could likely be handled with this same module, it's not my plan currently to do it that way. Mainly because the Hotel Room node the availability and quantity information is tied to isn't a product itself, just a regular node, and the product node will be created on the fly when a user goes to book a room.

So, it's something that I will consider for the future, but at least initially this is specifically to be a hotel room booking system.