Rok, Levine has had to make adjustments to his conducting because he is confined to a wheel chair. His ability to convey to the players what he wants has not diminished. Aside from actual conducting technique he has an uncanny ability to put into words what he wants and what the player should aim for that adds a certain clarity to the process. Levine conducted the run of "Falstaff" a couple of months ago and is scheduled to conduct Berg's "Wozzeck" beginning next month. You may find these video's interesting; he addresses some of those issues:
http://www.bloomberg.com/video/james-levine-returns-to-met-charlie-rose-10-21-IhodjYjSSh2VrNdXj2rHeg.html
http://www.metoperafamily.org/video/2013-2014/falstaff/watch/james-levine-rehearses-falstaff/2866059273001
http://www.bloomberg.com/video/james-levine-returns-to-met-charlie-rose-10-21-IhodjYjSSh2VrNdXj2rHeg.html
http://www.metoperafamily.org/video/2013-2014/falstaff/watch/james-levine-rehearses-falstaff/2866059273001