It's a good question.
I tried making it more active by using stock solution instead of 1+1 dilution, and that produced unacceptable fog levels. Looking back at the patent I think Anneman's idea was to balance the amount of borax with the phenidone, and there is probably a point of diminishing returns where there is no advantage to making it more alkaline because the quantity of developing agent is so small (or perhaps there is some other consequence, like pinholes with an acid stop). The high temperature I'm guessing is to keep processing times under 25 minutes.
Let me know if you try it and get interesting results.