Yeah, but he won't even wound you, if you don't deserve it. I just don't think Spike would come off as someone that Vash would deem he has to go that far with. Knives would, easily, but not Vash.
It just matters what they're fighting for. Vash has no pride, and let plenty of people "win" things they had no business winning. He wants to see people happy, more than proving his own thoughts and ways. Blame him for the destruction of a town, say he killed everyone in your favorite Month-themed district, he'll go along with it, as long as it means people can live in peace with each other.
No matter how many time I watch Trigun, read the Manga, or read of "VS" fanfics about him, he's just one of few action anime lead characters that really is almost everything BEFORE being a fighter. While most heroes have a "rage mode" that'll kick in to give them the desperation to survive... Vash's exist as Knives. I always feel the fate of Wolfwood is flat proof that Vash wouldn't be able to keep up his ways, if he wasn't an exceptional being.
Heck, the Gun-Ho-Guns had to off themselves most of the time, because Vash woulda set them free if it were up to him.
So follow up the fight with.. the fight Part 2? It would have overstayed it's welcome then, and boiled down to every other "this is the only way to resolve issues!" battle ever in anime.
I just feel like it does a disservice to the rest of the narrative to take the Hanafuda match as simply bets and watching her play. Granny's "This is WAR!" phonecall perfectly set the case that wars were not just fought through physical arms, but by connections, relationships, and the support of the people. Something a program could never hope to replicate, no matter how advanced the A.I.
Is there really any theme that hasn't been done to death? What I ask of my stories is to make the players memorable, and to make the conclusion a sensible part of the tale presented. SW's characters were better than most, and the roads they took to reach their destination were constantly surprising / refreshing. I didn't get that feeling of mostly watching simply for the animation quality, like I did with Akira.