The only way any of the Outer Planet Flagship missions is going to stay on schedule or budget, KISS is king. Inflatable, submersible etc - any significant deviation from a Huygens 2.0 philosophy is going to be a bad idea. The Balloon/Boat payload is part of the ESA/NASA TSSM proposal. The Lander/Balloon payload is part of the currently NASA only Titan Explorer mission. ESA doesn't have the resources to go overboard (pun not intended) on the boat. The balloon will be CNES in the TSSM.

Personally - I'd rather see the Titan Explorer design, with ESA doing the lander, CNES the balloon, and NASA the aerocaptured orbiter - rather than the current TSSM profile.

Doug