Making progress
The superconductor folks figured out a long time ago the link between isotope mass and Tc.
Unfortunately it seems that the process to enrich silicon is a lot more complex due to the lower mass, I am pretty sure that this will be a big problem unless these chips are made by the million and then simply selected by X-ray fluorescence (XRF) analysis in much the same way that flash chips are tested during wafer sorting and the bad areas mapped out.
I did read a fascinating article suggesting that "holistic" ie hole based qubits could be the next big thing (or not-thing) in QC research.
Hilarious that the absence of an electron can solve a nearly unsolvable problem yet people have known for decades that electron holes move much slower than electrons.
Maybe we should get a few botanists in at NASA, and nuclear physicists in the condensed matter laboratories for their "unusual" points of view?