According to many mainstream authorities, the widespread practice of Ashkenazic Kohanim outside of Israel of refraining from birchas kohanim is a minhag ta'us and possibly even forbidden biblically as a bittul aseh (annulment of a positive commandment). If an individual kohen wishes to be accommodate these views without causing a conflict with the congregation in which he is praying, are there any problems with his reciting birchas kohanim discretely, e.g. quietly, in his place, and omitting the customary hand configuration?
It would at least be a waste of time since holding up the arms and reciting the blessing aloud are required (ShA OC 128:14). In any event so long as no one called him up to bless, he isn't violating anything (ibid. :2).