Chris,
I think you have listed all the possibly available options.
I think option 3 looks best, as it will give same experience to user as
in case when javascript is enabled, but im try'g to implement it but
seems like browser won't take anything from response2, so we need to
change somehow response1 instance with response2 before we write to
client, now this looks like most feasible option to me as customer want
this only, now im just thinking best ways to implement
- We need to assume here that if customer send any request after we
start writing on the last response instance than there is no way to
handle it and this will again lead to problem, im sure this is like one
in maybe 10,000 case that will happen, but this step is so critical I
can't afford to make client see empty page.

Best option is though put a intermediate page like it comes in most
cheap airticket search sites so that user don't have option to send
another request, but this is not possible at this stage in product.,
Would love to hear comments from you.

Hemant