This is essentially IRV but you can equally rank multiple candidates, and they each get one vote. If everyone only uses the first rank, this is essentially Approval, so wouldn’t it actually be better? It’s also not a big shift from IRV. The biggest issues are that it still requires centralized counting (but so does PR) and that you can’t equally rank in most STV implementations, so that might confuse voters (having equal ranking allowed and not on the same ballot.)

The ideal system probably would allow scoring candidates in each rank, but that’s not practical.

Here is an example I found against ER-IRV:

45:Right=Left>CentreRight

35:CentreRight>Right>Left

20:Left>CentreRight>Right

First-preference tallies

Right:45 CentreRight:35 Left:65

CentreRight has the lowest tally, and so is eliminated then Right wins. This time no coordination was needed. As long as the Right suporters knew that Right had more first-prefernces than CentreRight, and a pairwise win against Left, then each individual Right supporter got an increased expectation by insincerely upranking Left from last to equal-first with no risk. This would also work if the numbers 45/35/20 were replaced with 49/48/3. I suggest the right numbers in your “paradoxical” row should be IRV1,ER-IRV(fractional)2, ER-IRV(whole) 5!

but just like in Approval or Score, the Left voters can stop this by equally ranking Center-Right with Left.