Why not just give yourself an extra combat phase after each opponent's combat phase? It was not immediately obvious that this was what you were doing. I read it as a Lighthouse Chronologist that, wait, what parts of the turn do you actually get? It was unclear.

Well, that and the ending phase. I'm not sure what we need a bonus ending phase for, though. You know... except for abusing a card with a benefit that happens at the end of turn.

That said, I'm not sure how giving yourself a combat phase after each opponent's combat phase would work, since it's still technically their turn... at least until you explicitly spelled it out that it was not, and then spelled out that their turn would return to normal once your combat phase ended. By that point, we're more confusing than the card as printed.

Maybe the wording "At the end of each opponent's turn, take an extra turn that only consists of an attack phase." would work. Or perhaps the more daring "At the end of each opponent's turn, take an extra attack phase."

Oh yes, of course. Giant Growth effects wouldn't go away without an end step. They would, however, go away during your next opponent's next end step. Bit of an odd trade off.

I don't know if the rules allow for taking phases during other players' turns.

Ueot effects wear off at the next clean-up step, so I think it makes intuitive sense for them to end at your opponent's end phase if you stick your combat in there. Since it's your combat phase, I think it makes sense for you to become the active player, in which case attacking works. It's grokkable at least

After discussing my idea elsewhere, they all shot it down too

I'm not sure your idea is impossible, but I do think the current way of doing it is easier.

Mine requires a rewrite of the rules defining active player. This works within the rules, but it feels off-color and is also confusing (for different reasons).

Ah. I have a hard time seeing those two points because I know the exact intent behind the design. Thank you for bringing them to my attention.

Yeah, this takes quite a bit of puzzling to work out what it does. "Skip all phases except combat and end phase of that turn" might be a bit clearer.

Also feels like it wants vigilance, if it's giving you lots of extra attacks.

I worried that giving it vigilance made it too good too easily, but then again, it theoretically a mythic legend...

I'll switch it to that wording.