As I understand it, the cap on the number of representatives is a matter of law. It is not in the constitution. That is what gives California so few electoral votes, proportionately, and Wyoming so much power. The Constitution states 1 representative per 30,000 population. It does not limit the number of representatives that a state can have. California would have something like 1300 using those numbers. So, we’re already in violation of the constitution, right?
I agree that would be unmanageable, but it does seem to me that overturning the Permanent Apportionment Act of 1929 and replacing it with something more equitable would go a long way to solving this problem. For instance, use the population of the smallest state as the divisor, rather than a fixed number. That would ensure a more equitable representation in the House and among Electors.