Howard would, in all likelihood, become the true cleanup hitter this team is lacking big time.
Lilly is not a good enough #2 on a team trying to make the playoffs, nor will he ever be. This club's best shot will come when hopefully most of Rosario, McGowan, Jackson, Purcey, and Romero pan into good major league starters, to which point Lilly will not be needed. At the same time there are no legit power hitters in the Jays system that will be ready within the next 2-3 years.
Lilly for Howard should be done in a flash if the Phillies are willing to make that deal.
As for having too many infielders. First thing's first, get rid of Hinske in any way possible, and that probably means buying him out. For the rest of this season, when Koskie gets back, we're looking at rotating 6 everyday players into 5 spots (including DH). Given the circumstances, this wouldn't be too devastating.
When next year rolls around, all pretending that Howard is here, Hillenbrand would be gone and there would be no problem at all.