Is a Smash Ultimate Deluxe even possible? I mean, Sakurai said a crossover like this would likely never happen again. All of the deals that had to be made to so many companies... For an Ultimate Deluxe, wouldn't Nintendo have to make a bunch of new agreements with other companies all over again to get the rights to a good chunk of the game?
Depends
It's possible that They might have negotiated for Both Ultimate, and Future Versions of Ultimate at the Same time
there was Speculation that Cloud was actually negotiated for Smash 4 and Ultimate at the same time, Though honestly I don't think these scenarios might have happened
I think in terms of Licensing, Because a Smash Ultimate Deluxe probably wouldn't be that much different from Regular Ultimate in terms of Gameplay and such, I think it be easier licensing on that front since there won't be as many new changes to the 3rd party Characters as compared to Smash 4 to Ultmate. This includes all the 3rd Party Newcomers added in, because instead of having to negotaties how this character will be represented in terms of Moveset, Trailer, etc, they already in the game, so less talks needed
However, I do think a big issue is that Depending on how the Companies get paid for their characters, a Smash Ultimate Deluxe would have issue because if 3rd Party companies get a Percent of the Profit instead of just getting Paid upfront, then that would mean every purchase of Ultimate Deluxe would not be as much Money for Nintendo as they may want it, because other companies would have their hands on it.
There's also an issue that I think There may not be as many people buying Smash Ultimate Deluxe, Perhaps citing Regular Smash Ultimate as enough. Remember that the OG Mario Kart 8 was on Wii u which did not sell much, Compared to Switch which sells Gangbangers, so Much more likely people Pick up Mario Kart 8 Deluxe. Mario Kart 8 Deluxe also doesn't have 3rd party costs either. Smash Ultimate Deluxe as an idea might not be able to pick up as much Purchases to offset how much money they pay to 3rd parties, and additional Content they might add to the game
There's also the Question is if this Content will be Exclusive to the Deluxe version of Ultimate, or will regular Smash Ultimate Player be able to get Access to this content?
At least for the Newcomers for a Deluxe version, I Imagine most of them will be First Party Characters, though there probably be some 3rd parties in there.