One of the big advantages of steel is zero deck leaks, ever, as welding down your hardware eliminates any chance of them ever leaking. No matter how rough it gets, you always have a dry bunk to sleep in at the end of the day, on a well insulated steel boat. There is no way you can get bolted down gear on a fibreglass deck that's permanently water proof, with zero chance of leaking. Fibreglass decks always end up leaking, eventually.
There is no way you can get a fibreglass boat as impact resistant as a steel hull. That is why so many former fibreglass boat cruisers tend to gravitate towards steel. The increase in peace of mind, when blasting along at hull speed on a moonless night, in a steel hull, has to be experienced to be appreciated.
'Many former' is an gross exaggeration. Most yachties expire leaving a fiberglass legacy. Nor are most sailors circumnavigators or transoceanic sailors. Most rarely get out of sight of land.
A steel cleat welded to a sunken hull with rusted holes might not leak, ever. Let the divers boggle. Impact resistance is actually a function of flexibility, not hardness. Unless we're talking a turret on a tank. I smell a mania, or a greedy agenda. But let freedom ring.
Maintenance is a given with any physical thing, whether it's a house, a vessel, or an auto. Or even a human body. So one must sometimes re-bed a cleat or other thru-deck attachment, big stinking deal - at least it's where you can detect and work with the problem without having to haul the hull.
Steel has its place in industrial hulls and like applications. But for someone who just wants to enjoy sailing with fewer worries, fiberglass is the way to go. There's new 'wonder glues' that essentially 'weld', melting the glass into an hermetic bond, for those wishing to seal their decks.
I have suffered with wooden toe-rails on a glass deck, so I know that mixing dissimilar materials, regardless of what they are, is a formula for trouble. Teak laminates may be pretty, but that glue dries out under tropic suns.