But, who's forcing the DM to do anything here? If anything, I'm giving less work for the DM. The DM no longer has to worry about what to do, if anything, with this patron. The player is not interested in playing that out. Why would you, as a DM, knowing that the player isn't interested, bring it into the game? Again, who is it for? It's not for the player. It's not for the other players. So, the only person it's for is you, the DM. You want to bring it into the game purely for your own enjoyment, knowing that the player doesn't want it.
Good grief, talk about mountains out of molehills here. We're talking about one small change to one character that isn't going to affect ANYTHING. But, now it's forcing a DM to play a game he doesn't want to play?
Meh, the player isn't going to have access to the backgrounded motorcycle except when he needs to travel from A to B. Note, the motorcycle is only backgrounded to the extent that it won't be stolen. If the player chooses to ride the motorcycle off a cliff, well, the bike get's smashed. The only thing that was backgrounded was the idea that the DM shouldn't mess with the bicycle off camera. I know right? Talk about player entitlement. What a jerk player for wanting the motorcycle to only matter when it's on camera. Sheesh, what a terrible player.
Or the pet. Again, it's going to be SOP and dealt with exactly once in the campaign. It's kind of like how you have one and only one random encounter when traveling from A to B because everyone at the table knows you don't want to waste a bunch of table time on pointless stuff. Again, what a horrible, power gaming player, who simply recognizes that fact.

"But what about an anti-magic shell"? Seriously? One, how often has that EVER come up in a game? Two, any time it might come up, what are the odds that the druid player won't have his pet snake out and ready?
Sure, scarlet, flaming monkeys might explosively exit my posterior at any given time, but, it's really, really unlikely.