Wash sales apply to capital loss harvesting, not capital gains harvesting, so you can buy whatever you want. If you were capital loss harvesting you could stay with Vanguard, and just buy something that is not substantially identical to VOO, such as VTI, but you wouldn't want to buy another S&P 500 fund from another company such as IVV. Again, this doesn't matter since these are gains, not losses.
I think you're on top of it, but just make sure you understand how capital gains tax rates work. The capital gain stacks on top of other income, so your total income including the gain needs to stay under the appropriate limit for your filing status to be taxed at 0%.
Remember to account for dividends that will payed out on your taxable investments at the end of the year.
If some of your income is earned income you can contribute to a traditional IRA any time until your tax filing deadline once you have final income numbers in order to fine tune your income to stay within the 0% capital gains bracket and within your ACA subsidy limits.
