Scars?

Gaping, open, unhealing wounds!

Build a second ap of equal capabilities without using js, and ensure that the first emphatically refers the JavaScript-less user to the second.

If, as your question three acknowledges, there is any class of customers/clients who may not be able to use your js version, then hard reality is likely to ensure that the members of that class will be the make-or-break demographic for the ap.

That said, you haven't given us much to go on about the target audience, nor about the required capabilities of the ap, nor clear rationale for using js. Have you satisfied yourself that these and other parameters actually dictate use of a technology tarred by widespread misunderstanding of its hazards? Have you satisfied yourself that using js is really necessary or desireable.

Just as it's said that "Hope is not a plan" so it might be said that "'I wanna' do it that way' is not sufficient justification for doing so" ...at least, not when a job, profit or the utility of the product is compromised.