Have you considered using a Webpart?
With a visual webpart which is essencially a usercontrol wrapped in a webpart you can add as much complexity as you want and you also have code behind to hook to events etc.
The benefit of using a webpart is that you can then drop it on a page, and use all OOB sharepoint access controls.
You mention that you want to develop a data entry reporting app. So something you can do is to create a subsite. Look all access to modify pages except to owners. Create all your screens by adding pages to the subsite and dropping webparts on it with the logic you require for each screen.
Also make sure you deploy the werbparts via a web feature that only is activated in your subsite, this way the webparts are only available in that particular subsite.