I want to know if it's possible to:

Use a regular saber and change the blue stance to staff stance while in-game (without changing to a staff lightsaber of course).

It's already possible to switch between dual to single and staff to single so i want to know if it's possible the other way around (single to staff) just by pressing the stance key?.

If so, anyone interested in sharing their knowledge on the subject?.

Thanks!

It can be done through code - not by default design.