I have already requested this to be an enhancement with SDF-36189 and do not see this in the "known issues" area. I would think that this would want to be escalated to a "known issue" since you cannot expect the customers to always select the correct template. IF they do not select the correct service catalog template, you do not have the ability to switch it to a different template, unless I have mistaken the Service Catalog's purpose which was to create a way to handle the customer's request in a format that displays the services provided using templates. So what would the purpose be of creating a Service Catalog with all customized templates only to not allow it to go live due to the fact you would have to close the original request (if they selected the wrong service) and create another request. I see this being show stopper to ever creating a Service Catalog! Should just stick with the incident templates that actually work if needed to change which template applies.
Unhappy with the design of the Service Catalog!