Houston needs to free up cap room for Howard and assuming they can get him, they'll want to surround him with shooters. Any chance we'd have in landing Asik would have to involve Pierce.
I think they would consider a deal that nets them Pierce (who will be waived), Jason Terry (shooter), and Sullinger (decent shooting big) in return for Asik, Thomas Robinson, Royce White, possibly Terrance Jones or Motiejunas, and expiring deals like Delfino and Aaron Brooks.
That would probably free up enough for them to give Howard a max deal. However, they could free up even more by doing a deal without Terry.
Houston receives: Pierce, Sullinger, future Boston 1st
Boston receives: Asik, T Rob, Royce White, Delfino, and Brooks