I have seen a Fed bust a CA for failure to plan a descent in icing conditions so that all restrictions can be met, even with an increased power setting. This basically means getting down early. In the CRJ there is yellow "min power" marker when the wings are on, and this Fed considered it a violation to reduce power below that setting while in actual icing conditions.
If the arrival is constructed so that it's just impossible to do the restrictions in your aircraft in the given conditions, then state "unable". Maybe they need to redesign their approach to accomodate the airliners that use it. Probably a good idea if you give ATC a heads up if you expect to be unable.