Here is what people have to remember, ADA requires businesses (including theme parks) to provide accommodations at no additional cost to the customer (or guest in this case), so as far as the DAS goes, here is what ADA would have to say about this:
If a Guest without a disability can do the following: | A guest with a disability would have to be allowed the following: |
Get a Virtual Queue or pay for a single use lightning lane and come back to a stand by wait time (or have lightning lane access if paid) | Get a virtual queue or pay for a single use lightning lane and use a DAS to have an alternative place to wait for an equal amount of time or less (or have lightning lane access if paid) |
Use a stand by queue at no additional cost | Be able to use a DAS at no additional cost to provide an alternative place to wait. |
Can only access the attraction by paying and coming back to a stand by time | Must still pay to access, but when returning must be offered an alternative place to wait. |
In short, if someone without a disability can wait for an attraction without a boarding group or paying, then the DAS must provide a return time, anything short of that would be violating ADA, unless Disney completely overhauled the access system and then it would be based on whatever the new system is, but it would still need to provide access without additional costs. And since there is a Lightning Lane at the individual paid LL access attractions, there is a feasible alternate entrance, so the exception I am about to mention cannot be applied here.
Allowable exceptions are if it is not technically possible to make something accessible, for example a fun house with a moving floor would not be technically able to be accessible; however, even under those circumstances as much as can be made accessible must be. Let's take the fun house example, say the beginning and end cannot be made accessible, but there is a large section in the middle that can be accessed through an alternate entrance and exit, then that must be done.