Patternless is selective breeding of striped, also reffered to as vanishing pattern. So, the likely result here is that the first generation will be Amel, 66% het snow that has a broken stripe. Your second gen will be dependant on how the line is bred.
Bred back to the snow, the offspring should be snows with lightly borken stripes, as patternless isn't a gene, but an expression of a gene.
Bred back to the Amel, you should see amels that are 33% het for snow and have one third to over one half of the stripe vanishing.
Bred back to their siblings, the results should be snows with half or more of the pattern vanished.
Feel free to correct this if I am wrong, guys, but this seems to make sense to me genetically. Is it a waste? Well, if you are looking for solid white snakes, this breeding schedule will not produce them. If you are looking to get snows with a good expression of the vanishing-type stripe gene, this will be worthwhile. He will have to determine if the offspring listed are worth the 4ish years, cost af snake feeding and electricity for heat/light (if applicable), and the risk of losing your breeders due to complications in birth, which is always a concern.
For me and my tastes, this is a waste, as I like color morphs and don't care for stripe or vanishing patterns. But that only works for me. If that is the result he wants, or the pattern is one that he's trying to create, then it is well worth his time. It will have to be up to him, and hopefully this bit of a schenario breakdown will be useful in making that determination.
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1.1.0 Dumerils Boas
0.1.0 Anery Cornsnake
1.1.0 Amel Hurricane Cornsnakes (66% het Snow)
0.0.1 ?Mystery? Albino Plains Garter (WC)(Ask for pic/details)
1.0.0 Apricot-phase Plains Milksnake (WC)