This should be stackable with enough parameters
If you can clearly communicate what the player's goals are with their character, developing an option for optimized damage based on those parameters should be doable.
I would definitely highlight that simpler is better for this character as part of the process and make that one of the requirements.
But we ...
The requests for clarification in the comments (now the chat) are entirely reasonable.
Is this really a request to bake these two builds off at level 20, or is this a build that will be "grown through" over the course of a character's life (in which case lower level weaknesses should be taken into account), and is there any guarantee it'll reach level 20?
Close #3 as a duplicate of #1, and fix the dupe target of #2
It looks like #1 and #2 are identical to each other, and one of them should indeed be marked as a duplicate of the other (as you note).
However, the two questions are not quite the same as #3, which is a more specific subset of the other two; whereas #1 and #2 present the general question of ...
If you think the general question is valuable, ask the general question separately. It will (probably) get closed as a duplicate, which leaves a pointer to the existing answer (as you want), but lets the normal site mechanisms answer it.
The question's fine - but your proposal doesn't change what you're asking.
The title of your question - "How can I use a somatic component while holding a weapon in 2 hands?" - makes it clear that it's a general question. The specific spell is what prompted the question, since it both has a somatic component and acknowledges the possibility of using the ...
The 'better' question should not be closed
'Better', of course, being a bit subjective but including which question most clearly spells out the problem, which has attracted the 'better' answer(s) etc. Older is better than newer if everything else is equal(ish).