Thing is, after the ceremony, everything becomes set in stone, so to speak.
No appeal could now take away Verstappen's title, and neither can the FIA now disqualify Mercedes, I hadn't thought of that myself, so whatever they do would have to be a monetary punishment or something that applies to next season.
Maybe that would be even funnier, if FIA dishes out a punishment that pretty much gimps Mercedes from the get-go.
In an ideal world, the punishment would be similar to the fate that befell anyone whose car broke down on one of those Top Gear specials, and who was then forced to complete the remainder of the challenges in a Fiat Punto, or something equally shit. A season spent attempting to warm the tires of a Mastercard Lola, by frantically blowing on them, would be a humbling experience for Hamilton and amusing for everybody else.
I daresay the actual outcome will be a stern warning and a fine. The FIA can't be seen to go in too hard. A pre-season driver and/or constructors points deduction, or first race grid demotion, might also blow up in their face if Mercedes lean into their underdog status and spin a narrative around clawing back the loss against unfavourable odds (while failing to acknowledge their massive team budget and resources).
In the FIA's shoes I would begin by requesting formal public statements from Mercedes and Hamilton, explaining why he failed to attend the Gala. This would allow the FIA to appear magnanimous while placing Mercedes and the former World Champion on the backfoot.
If either Mercedes or Hamilton refused to acknowledge the request for a written explanation, then this snub could be used as justification for a harsher punishment, for bringing the sport into disrepute. If they were to claim they did not attend the gala in protest over the result of the race, then they would have to explain why they withdrew from a formal dispute, and instead chose to express their disagreement by failing to turn up at the Gala - an act that is regarded by many as petty and unsportsmanlike behaviour. If Mercedes then claimed they withdrew from the dispute because they believed that the process would be biased, that would potentially shine a bright light on past decisions by the FIA that were either resolved in their favour, or occasions where accusations against the team we're not investigated properly, if at all. They would end up coming across as entitled and devious.
Essentially, both Hamilton and Mercedes would appear childish and incapable of losing with grace if they failed to issue words to the effect of: 'We were all left deeply butthurt by the manner in which the championship concluded, to the extent that it would not have been comfortable for us to remain sitting down at the Gala for long periods. Regrettably our engineers were unable to create a solution that would have eased the tension on our ravaged buttholes, leaving us with no option other than to withdraw.
The more corporate 'sorry, not sorry' double-speak, and media training platitudes, that Mercedes and Hamilton engage in, the more pathetic they will appear. It's probably beginning to dawn on them now that throwing their toys out of the pram in public was a poorly thought out strategy.
Hamilton might do well to recall the numerous occasions where Bottas has been made to eat shit in order to assist him in his world championship bids, and has done so with humility and mostly without complaint.