Realistically speaking, a 12P+0E design will be a regression in multithreaded performance against the existing 8P+16E processors in controlled, benchmarked environments. However, the extra high performance execution units should prove very useful in many more real-world scenarios, without the drawbacks of the 12-core Ryzen processors' split CCDs or their X3D counterparts' imbalanced hardware configuration.
E-cores also come in clusters of 4, which roughly take the same die area as one P-core. I believe you wanted something like the Royal Core design, where there are P-cores and a couple of super big cores. This was supposed to be Beast Lake and to be marketed as Core Ultra series 4 (after Panther Lake/series 3, which would be Arrow Lake's refinement still on LGA 1851), but it was unfortunately canned last year.