Some liveries allow custom numbers but would it be possible to just have the custom number on the cockpit panel for liveries that have a painted on number on the fuselage?

I use an N number that I used to fly IRL with on all my planes when the liveries allow it but I would like to see my N number in the cockpit all the time, regardless of livery. 

Hope that makes sense.

Thanks

That depends on the livery I guess. Some liveries also come with their own panels which need to have an option to show the registration. Perhaps you have to edit the panel.cfg to make that happen.