I got 3 rods right now and I'm not planning on buying any more for a good while:

*A 7 foot UL/Moderate 2-piece Fenwick Eagle with 5lb P-Line, that's normally used for soaking worms and jigs for bluegill 

*A 6'6 M/XF 1-piece Lews Speed Stick with an empty reel that I'm probably gonna put 20lb braid on, use as a texas rigs / weightless plastics rod

*A 6'6 M/F 2-piece Diawa Fuego with 15lb braid and normally a 10lb fluoro leader, use as a hard baits rod

 

I'm wanting to get into Ned rigging, but I don't wanna bother constantly messing around with setups for one technique. The closest thing to what most people use that I have is the Fenwick, but I'm concerned that it's too wimpy and doesn't have the backbone for good hooksets. Or what if I'd just tie a light line leader on one of my braid rods and use it? 

The M/F is going to work far far better then an UL/M.  I have tried to fish a Ned on an UL a few times and I was missing a ton of hooksets.  Even with the super small jig hooks I prefer, I was really struggling.  

I've used a 1/12 oz ned rig on a L/F and it seems to just get by, at best. I'd use your M/F rather than the UL. The UL probably won't have enough backbone as you mentioned. Spinning reel preferred.

 

first time I took my crappie fishing neighbor bass fishing all he owned were ultralights. 

I gave him a couple shroomz heads and a bag of TRDs. he caught a ton of bass, only losing a couple.

 

setting the hook on a shroomz head is not much different than a crappie jig.

an ultralight will work with a ned rig, but if you hook a large fish, you may have your hands full.

What are you fishing for? If you want to lip hook pan fish with a Ned Rig, your UL will be fine.  If you want to go after bass, better use your 6-6 MF rod.  

You can, but it won't be ideal. Setting the hook and getting the barb set will be the biggest issue. 

Yeah, go with a ML/F or a M/F. I use a Dobyns 702sf dedicated for the Ned rig.