This can be made much, much simpler. If you are really scared of rebalancing, choose one of Vanguard's target date retirement funds. They're low ER for this type of fund.
If instead, expenses are your focus, so traditional 3 fund portfolio and rebalance on your birthday. This is 15 minutes of work per year. You know what? If you instead don't want to rebalance that often, don't. Do it once every 5 years! That's 3 minutes a year.
What I do is hold all 3 funds in a rollover IRA, because I'm old and have rolled lots of 401k's into there. Having this account, I can do the "sell to buy" in that account on my birthday without generating any taxable events. I keep track of my asset allocation on a simple excel spreadsheet.
There ya go. If you have other accounts (roth, taxable, iBonds, spouse's accounts), each one can be in a single fund or ETF (what I do). You NEVER have to sell from any of those accounts before retirement.
Every *good* brokerage house has some number of *good* low cost funds. Fidelity and Vanguard have great, low cost mutual funds. Schwab and TDAmeritrade have great, low cost ETFs.
I have accounts at Fidelity, Vanguard and Schwab plus a bunch of iBonds. I manage it as a 3 fund portfolio and it is very easy to manage. It's in the 2 comma range and I see no reason to make it more complicated at even bigger values.