Yes, you are completely right about this. And I can figure it out how to make them working without problem.
BUT: I keep on external drive for a simple raison: secure and encrypted. As have 1T space, can hold as today size if block chain, 5 different bitcoincore.
Or other way is to merge all wallets, what I was trying already, but without any success. Exported by dumpwallet, and got only error messages and the main wallet.dat intact and same size.