Even without a dual-phase lightsaber, you could use a double bladed lightsaber. Bondar Crystal in one blade, Lum Crystal (or what ever) in the opposite. Rig the switch so the middle setting is off and either direction turns the corresponding side on (trading the ability to ignite both sides with a reasonable way to excuse the swift action flip), maybe include an alternate method of achieving activation of both ends. It would certainly be long handled, meeting that prerequisite. Now dual-phase is certainly easier, but if the GM is not allowing/using JATM, it is a functional means of accomplishing the same goal, with a certain jury-rigger's panache.

Suggested switch pattern
1
/ \
2-3-4
|
5
1 = both blades ignited
2 = lethal on, stun off
3 = both off
4 = stun on, lethal off
5 = off + safety engaged.

the lines represents the path the switch can follow. This does mean that dual activation isn't possible from off with one movement, this is a safety feature not an oversight. 2 is toward the Lum Blade, 4 is toward the Bondar blade.