Having a requirement where we should not allow all special character except like(_,-,:,/) as input value for ddoctitle field.
The logic used for restricting file types during check-in can be modified and applied for ddoctitle as well .
Have you tried using a global rule on the dDocTitle field?
Created a custom component and add these validation over there as dDocTitle field not there in information fields.
Thanx for the update. Custom Component seems like a good way to handle that. Cheers.