I've been saying this for a few months now. It'd probably cause chaos but I'm kind of at the point where the status quo is the biggest problem we have in governance. Along the same lines, I'd push to make Puerto Rico, Guam, Samoa, the North Mariana Islands, the Virgin Islands and the District of Columbia states. Puerto Rico would rank 30th by population, ahead of 20 other states and DC would rank ahead of Vermont and Wyoming. You'd probably get fought down to Puerto Rico & the VIs, Guam Samoa and North Mariana being a part of Hawaii and Columbia... but that gets you four new senators and five new representatives, all likely to be Democratic. And it only requires a simple majority.
Along with these changes I would really love to see the repeal of the Reapportionment Act of 1929. It effectively caps the House at 435 members, regardless of the population increase that has happened since then. Once the cap is removed, more populous states will be truly represented like they should be and it would be unlikely that Republicans would ever be able to control the House ever again.