Many of the products have 3, 4 or even 5 option dropdowns for all of the variant choices.

We're seeing noticeable lag in the postback after a dropdown selection is made. So much so that the shopper can actually be in the middle of choosing the next dropdown choice when the control unexpectedly refreshes. This disrupts the selection process on that control. Since it happens on every dropdown, the issue quickly frustrates the shopper.

Is there a possible workaround?

We're fine with the shopper being forced to make linear dropdown choices. We just don't know how to identify the dropdown controls in play and where in the sequence of dropdowns the shopper currently is.

Thank you for the example link. That was my thought as well but I couldn't think of a way to easily do it.

So basically wrap all the option dropdowns being rendered in one fieldset, then modify the onchange() in app.js to disable the whole fieldset after a selection is made. The postback fires, the AJAX refreshes the controls and now the dropdowns are unlocked again. Am I on the right track?

Try disabling the form feild after submit is called. You will have to define ajax onBegin function where you will disable the fields and in onSuccess you will enable the fields.