I considered LiFePo as a workaround, it just has 2 downsides.
It does not work for all li-ion chemistries, as LiCoO2 is virtually depleted at 3.6v resting, just slightly better at 3.65.
And it only works in 1 direction - charging - so I need to discharge every other cell first.
This is strange, so many analyzing chargers out there lately, opus, xtar, nitecore, but seemingly none with a storage mode.
Unless you store your unused batteries for years before using them again, there shouldnt be too noticeable degradation of capacity.
At least my NCR18650B’s are still good after years of storing them fully charged and only later learning about somewhat better lithium battery storage techniques.
These are estimates, as it depends on cell chemistry and separator used. But if you want to get as much from your cells as possible, and I surely do, storing at ~40% is the way to go.