Even if we already include areas/places in the routing there is still some work to do as we need to cross the polygon and the way along the lines might be suboptimal.

http://comments.gmane.org/gmane.comp.gis.openstreetmap.region.at/5213

http://openplans.org/2012/06/b-roll-david-solves-the-plaza-problem-with-help-from-de-berg-and-matt-conway/

Think about it: Instead of pre-calculation: use spline and post-processing while or after path extraction