Kled barely needs to melee. Your focusing on the wrong part of the Kled support.
Kled doesn't need much gold to perform well just start building
and after that he's set to build into whatever tanky stats you feel like.
Kled isn't an all-in champion.
Pantheon is an all-in champion because he constantly can just W,Q,E and that's all pantheon needs to do.
A good Kled would never all-in since most of Kled's abilities don't do much damage when chained together. The playstyle of a Kled support would be to poke Q in lane and if the Q hits Kled would try to get the target pulled in then unleash the full combo on the target for the ADC to finish off.
It's not doing an all-in without landing that Q and making sure that ADC is ready OR having R up to E into the enemy and set up a kill for ADC to finish off.
Kled at most needs a small income of gold to be effective since two of his abilities set up for kills easy. E even leads into R to give an easier time setting up a kill.
Pantheon support didn't work because pantheon is a fighter/assassin who needs to get ahead early with kills and CS to survive.
Kled fits in to 6/6 of the points you stated in your Pantheon post.
You seem to have a lack of knowledge of Kled. This isn't your fault necessarily however it seems your not educated enough on what I'm talking about to understand how it would work.
Think of it like Darius support. Q on Darius and E on Darius both help adc get kills and get fed. Even with a lower gold income Darius doesn't fall under the curve in toplane if he's behind.
I could keep naming tanks all day and how a lot of them would work in support. Even Yorick support would work if the Yorick had
And Built
second. By midgame Yorick's ghouls would be deathtraps from all the slowing (I'm talking about both upcoming rework Yorick and current Yorick BTW)