Are you sure the delay is really 10-15 seconds, not an exageration as that'd be a very long delay. I will tell you that all of the newer cars do normally have a noticeable delay when given full accel and it's not just Volvo, I've noticed that on MBs for many years and others as well.
If you are exagerating the time and really mean the temporary delay instead, there's nothing that will ever cure that as for whatever reason, it's a "built-in" feature and apparently engineers have there reasons as to why it does that. Me, yeah I'd prefer an instant throttle, shift response in my cars too but the newer cars don't do that.
If on the other hand you're sure that there is a real problem, something that's abnormal, have an experienced Volvo dealer master tech (not a service writer) go with you on a test drive to get his input on that. If it's like I'm assuming (above) and it's just like any other new V70 (which they should be willing to let you compare as well), then you'll know that that's the way it was designed, built in and not cureable.
No dealer or VCNA people can change anything that was designed into the car if it's "normal", like all the other new V70s.