When you build process for others, and especially when that involves a service level agreement (SLA) from others – recognize that this is a two sided arrangement.
In exchange for getting your requests in the right fashion, you have to meet your requestors halfway with communication and clear expectation of delivery. Recognize the reason why process exists in the first place – to establish predictability. If you do not reliably honor due dates or communication in that process, don’t be surprised if people decide to take a shortcut to bypass your process.
If you are working to get people to submit requests a certain way, make sure that request queue is not a black hole. Establish clear expectations on what happens after a request is submitted. Give people visibility to what’s in queue. Communicate regularly on status updates.
Anyone can build a request form to dump people’s requests in a list they can look at someday. But it takes thought and planning to get people to keep following that process.