Maybe not, but possibly the next owner might. Or... if he damages the bracket by accident he'd have to remove it. Plus, and I know that you know this, so I'm just mentioning it really for the OP... things on a boat need to be resealed every so often. 5200 is just the wrong thing for this application where an adhesive just isn't needed.
We go through this discussion a lot on the forum regarding adhesives and sealants. Honestly, I really don't know what is best in some instances. For example, I think we agree that 5200 is appropriate for below the water through hulls.
I also feel that it is appropriate for backing plates. Dive ladder brackets? Hmmmm.I can argue both sides, 5200/4200 type adhesives and Life caulk types of sealants. The later can be removed more easily but probably flexes more under stress. That can be good if the fixture is subject to movement but if the fixture doesn't want to move, the adhesive will provide additional strength to the bond. I have a dive ladder on Myotherboat and it is subjected to very large forces when boarding. Using a sealant might be more prone to movement (twisting) than an adhesive like 5200.
If mating surfaces are likely to move in relation to each other, like in a deck hatch, I would use a caulk. If the part I am sealing may need routine maintenance, I would also lean towards a caulk.
So, chime in on your suggestions for the following:
Gunnel mounted rod holders
Hardtop mounting bases.
Backing plates in general
Hardtop VHF antenna base
Through hull transducers.
Fill fixtures, gas, water etc.
Deck plates
Pulpit to deck
Scupper drain tubes
Sea cocks
Engine mounting bolts.
Motor bracket to transom seal and bolts
Underwater light fixtures.
Things I missed.