The kanji 網 and 綱 are both said to be composed of the same two radicals, 糸 and 岡, but this is misleading because the kanji are not also the same. Instead, 網 should be said to be made of 糸, 一, 冂, 丷, and 亡 to prevent these easily mixed up kanji from being more easily mixed up.
I’m not Tofugu, but based on ideas they share here, which you can also find discussed in, for example, Remembering the Kanji, I think five radicals is more radicals than is ideal.
If I needed more help distinguishing the two kanji, I might consider whether some combination of those four alternates you suggested is worth becoming a radical for my personal use, and following WK’s methods make up a story and a name for it.
I wouldn’t mind if they made a new radical for it, but I think interpreting it as five existing radicals is a more realistic approach. It may not be ideal, but sometimes, there’s no other way.
懲 is also said to be made of five radicals, although the four on top make up 徴, a separate kanji. They also state this in the mnemonic. I’d also be okay with that approach for 網, combined with the five radical interpretation, so long as they also differentiate 罔 from 岡.
It’s always a bit rough with those components that are barely used anywhere else.
At least as long as 亡 is recognized as a part of 網 it should be a good compromise.
亡 罔 惘 網 魍 is a phonetic series with readings ボウ・モウ.
Seconding a request for a more careful treatment by the content team for these two. I’m certainly struggling with retaining and differentiating them.