It is not supposed to be memorized. Mnemonics, despite what the term may sound like, is a way of converting a hard-to-write bitstream to a human-readable string so that the user can easily write it down on a physical medium and later on enter it in a computer program.

The entropy size for BIP32 is between 16 and 64 bytes and I believe the seed that bitcoin core uses is actually 256 bits which means if you convert it with your scheme you should end up with at least 70 values.
The problem with this idea is that memorizing this many values is very hard for people unless they have eidetic memory. As time passes you will forget parts of it or the order of some values and will be screwed.