One year later, I feel like I should update this. Pi-hole has moved quite a bit in this time, even though much of the movement is in the interiors and mostly hidden from the end-user. However, parts of the changes enables us to redesign critical parts. I’m not yet saying that we are going to have it in the end, however, we already have a working variant of the FTL daemon which is actually able to do per-client black- and white listing. Even per-client blocking lists is already implemented.
There are still technical details to clarify. While there are important benefits, such as a massively reduced memory footprint, there are also downsides, one being the notable degraded regex performance. This is caused by us not being able to apply some performance tricks we invented for our current universal (as in the opposite of per-client) implementation.