I'm definitely in the camp of 'no ante' as a main mechanic, mainly because of the weirdness of having to set up a collection to begin with (and that's a whole other can of worms). That being said, I do think that sort of... Banking on the 'trading' aspect wouldn't be too bad, either?

Start with a deck, no collection (or maybe a small one), open packs/sets/boxes/cases/whatever, build up, trade. There's no external economy to have to fret about, so you don't end up with the 'value on X/Y/Z' problem, and if someone gets something your character might want, then that's something to manage in-RP. Maybe holos actually exist in-universe and you want to be extra, idk.

Starting with far lower stakes and scaling up rather than starting with them being huge kind of lends itself to that, I'd think. Establishing the players as a group of people gathering from who knows where is fine, and given how big the game is culturally in-universe (as was mentioned prior), I don't think it'd be unheard of, per se.

Battle City definitely lends itself to more of a one-off in my head, if not just a single arc. The stakes are definitely lower compared to... Well, pretty much every season thereafter, but going down this route also brings in to question how slow the opener is going to be + how fast the players want to scale into the bigger stuff. A smaller-scale opener to establish a baseline could help.

It might also incentivize characters having more reason to interact with one another rather than doing the YGO equivalent of being a murderhobo, as despite personal intentions to be there, it's not like the characters themselves have any inherent reason to stick around unless there is made to be one. I could be wrong, of course, but that's the way I'm seeing things. Wasn't most of Battle City also spent with the cast sort of roaming solo, too?