I have been thinking of this project!
I was driving home tonite and the timer project came into my head.. I believe it was a Mallory timer, but often times, they actually had the Hobart part number on it and not one of their stock numbers.
How about getting a time delay relay which will interrupt the timer motor for you and hook it up to the WASH pilot light on the panel? Of course that will take some additional circuitry or one that will only cycle once. And if you should add another item and open the door, the light goes out and then relights so it may delay the wash even more. So you may have to think that one thru.
But again, is the problem with the short wash times of 5 minutes each, too short for your enzyme "packet" to dissolve?
If it is, why not just use a good, old fashioned, powdered detergent? And like I said earlier, I have no problem with the cleaning in my Superba using Cascade Extra Action with the grease cutting power of Dawn! or even Cascade complete. Due to extreme temp losses on my below slab hot water line,I will select low energy too but then switch to Sani cycle for the added heat at the end.This insures totally dried dishware as well.
The infinite switch works just like one used on an electric range, depending on where you set the dial, it varies the time on and off of the device it controls. The one used in the dishwasher was preset, that is, no means of varying the amount of on time.
Another option for you would be to install a small toggle switch somewhere like on the bottom of the lower front panel which would interrupt the timer motor so you could make the wash as long as you like it! Of course, that necesssitates your own intervention as well.
Again, I can't imagine how poorly your machine is washing that you would want to extend the cycles. I am sure you can poll anyone on here with a similar machine and they will all concur that it is a very satisfactory washing machine out of the box! And if extra cleaning is needed, they use the soak and scrub or heavy wash cycle with the heavy and sani cycles being identical except for the final rinse temp.