It looks like a bit crazy idea, but Vitis (or similar plant growing as a liana) looking for natural support may equally well use Heracleum as such? Vitis vinifera is a liana growing up to 30 m in length, with leaves up to 20 cm long and broad. There are likely many problems here (e.g., proper timing), however. What do you think about usefulness of such form concurrents?