Upload & Sell: On
A universial fit L bracket has a big issue of possibly rotating and coming loose while in use, especially if your camera is in the portrait orientation. To "avoid" the rotation issue, some people may tighten the mounting screw extra hard to try to clamp the bracket on better, and possibly may overload and damage the bottom of the camera. Custom fit brackets have surfaces that project up above the bottom of the camera and cradle it, and those surfaces provide the secure good fit that allows you to only use "normal" tightening of the screw.
In additon, a universial fit L bracket may end up blocking access to your battery compartment, either on the bottom, or on the side of the camera. And also, the universial fit L bracket can easily block connectors on the side of your camera. I for one use a remote release very often for tripod mounted cameras, and very much appreciate the custom L brackets I use that provide for that.
You might want to focus on just one camera, or perhaps two of your three cameras, and go for a custom L bracket. You can likely get one used in some on line way to save money, and can perhaps sell things after you need is over.
Another compromise is to just get a bottom only custom plate or two, and then use the side slot in your ball head to get to portrait orientation. A third way to go is to get a bottom only multi fit plate that has a ridge to help prevent rotation. The Really Right Stuff BP-CS plate is such a plate. You could then move that from body to body as needed for your three bodies. And a bottom only plate obviously has no interference issues with the side of your camera.
The need for a good custom fit L bracket will always depend on your shooting style and how often you want to use a tripod with non collared lenses, but I know I could never be without one for 70% of what I shoot. Getting a nice custom fit L brakcet for each camera I buy is just part of the way I do things, and I would never consider going back to the old days when I struggled with tripods and mounting systems.