Not constitutional, but the number of justices is set by a current congressional act. It would only take the Congress to up the number to 11. 11 makes sense since it is the number of US Federal Court district’s. This would put the USSC inline with the representation in the Federal Court level. At least how it would be sold. I doubt a constitutional amendment will ever be passed setting and fixing the number if USSC justices so it will always be in the hands of Congress and therefore the people via our representatives. So no you can’t just disband the Court you can only change it to reflect a growing nation. FDR tried court packing he failed Congress is hesitant to break with precedence since if one side raises the number the other side will surely follow as soon as they can. Setting up a arms race until a constitutional amendment would have to be had or a total collapse of the system.
Let’s dissolve the Supreme Court. What now? The Federal Circuit Courts of Appeal are now the highest judicial authority in the land. So if an issue comes up in two circuits and they have different outcomes then there is no resolution until a federal law is passed resolving the issue. If no such law is passed then the issue remains unresolved from a national perspective. Maybe one circuit will say abortion or concealed carry is fine in that district and the other circuit may uphold laws banning these things completely. For those who are philosophically disposed to think equality of outcome is the greatest good, this should be unacceptable. It is as if you had multiple areas (11 in this case) with their own set of laws. These people want uniformity! The idea of 50 states, each with their own set of laws blows their fuses. And that is precisely what has happened here - the issue has been returned to the states.