IP address of pool member servicing a connect request in response header?

Hello Asteroidia.

Sure you can.

when HTTP_REQUEST {
	set clientIP [IP::client_addr]
}
when HTTP_RESPONSE {
	HTTP::header insert Client_IP $clientIP
}

REF - https://clouddocs.f5.com/api/irules/HTTP__header.html

KR,

Dario.