Guise: "I Call <X> to the Stand! No, not that one!"

Simple question: Can Completionist Guise's power swap the Representative of Earth with a variant of itself?

- Related question: If so, does that then change the max HP of the Representative to the card's innate HP, or does Representative of Earth still cap it to 10?

I would say yes to swapping.   As to the HP I'd say they remain at whatever they were at and their HP cap would still be ten since they are still out associated with Representative of Earth.

It should, but that card would still be next to representative, and thus the rules would still apply.

We’ll need to wait for the video game to know for sure but a literal reading of both cards suggests to me that he can and that it would change the Max HP of the representative to the character card’s max HP.

Why would it change the Max HP?   They are still associated and only out there due to Representative of Earth.   Waiting on the video game for the answer could be a while as I imagine Completionist Guise is probably one of the last variants they are going to do.  

Representative of earth changes the max HP of the hero next to it as part of it’s “when this card enters play” text. When Guise swaps out the hero Representative is already finished entering play, so Guise’s power should change the representative hero’s max HP the way Guise would change the max hp of any other hero character card he uses his power on.

I can understand the point but I wouldn't rule it that way of encountered on the tabletop.  The card doesn't say when it enters play set its max HP to 10.  The statement on the card just has a singular sentence stating what the max HP is and switching it out would not change that as the card is still next to Representative of Earth which lists a max HP.  

If I had to guess… I’d guess that the wording on Representative of Earth will be changed slightly in the digital version to work the way you are suggesting.

This seems like an interaction that wasn't planned for. When Celestial Tribunal came out, we didn't have any heroes that could manipulate variants. With Completionist Guise out, I'd say Celestial Tribunal will continue to work as it was designed to.

Now, the way I would literally interpret the interaction is that the new variant would act as though the game started, and its maximum HP would be the HP printed on the card. Representative of Earth is worded in a way that leads me to believe that "setting its current HP to 10" is an action that happens once. It doesn't seem to be a constant check. If it were, I'd imagine it would read "That hero's maximum HP is now 10." In that way, it feel more like a game rule, and not a one time action. I agree with Skippy though, the next sentence "If that hero is incapacitated, the Earth is sentenced to destruction. Game over." is tied to that hero altogether, and no change in variant would matter.

I would personally rule in favor of the former scenario. It would still be 10, because that's how it would work as intended.

If you swap out a hero character card that has a card beside it that says "the target next to this card" on it, that new Hero Character card is affected the same way as the one you replaced.