How are the holders aware of the Solar Legacy wish thing?
I'll reveal it at the start of the RP in a long exposition by a character who may or may not be otherwise irrelevant. Or maybe it's some inherent knowledge. Perhaps their cards whisper to the owners.
Is the 'wish' section the thing they're going to ask when they win 15 times, or is it a symbolic thing?
A little bit of both.
Can someone refuse to summon their legacy when it urges them to through shere force of will?
Yes, but it would be extremely painful.
How much duel energy is drained?
Enough to be plot relevant.
Can someone refuse to put their legacy in their deck?
Yes, but it will always find its way back and may likely end up as a drawn card regardless.
Do the Solar Legacies interact with their duelist in some other way? (e.g. the dimension dragons with their yu-boys, Judai and Winged Kuriboh, ...)
Yes, the cards interact with their owner. To what degree, however, is on a case-by-case basis.
What stops someone from dueling the same guy 15 times in a row every time they get their energy back, by force if needed?
The duel energy doesn't replenish until someone makes a wish.
Does a duel between Solar Legacy holders turn into something that physically hurts?
Not necessarily, but this game has Solid Vision with mass, so it is possible to hurt other duelists. The Solar Legacy cards are also artifacts that hold some kind of magical power. Take that as you will...
If one disobeys their Solar Legacy, could it choose to leave you?
For the most part, a Solar Legacy has a mutual relationship with their duelist and really can't grow without them. While I can't necessarily force a player to do such a thing, a Solar Legacy can sabotage games by not showing up at the right time, becoming a dead draw, or might even influence draws so the player draws into something they don't need.
Thinking of throwing my hat into this ring, if it's alright. I'm planning on playing a movie buff type with a ramshackle Kaiju deck.
Sounds good. Kaijus might be interesting- and also possibly force other players to play differently.
@KOgaming: Righty-o, here's what I've made.
Duel Disks are solid vision. Also, for consistency's sake, the game will be referred to as Duel Monsters. I've talked to you about your deck in PMs, but I still think a ritual user shouldn't have so many synchro monsters.