One of the issues that has often come up in our campaign is jumping onto or climbing onto monsters. For example, when fighting dragons, one of our players has repeatedly expressed a desire to climb onto the dragon's back. However, there are no rules, to my knowledge, for jumping or climbing onto a monster and the rules for mounted combat are limited to willing mounts.
How would you create a set of rules for D&D 4th Edition to cover jumping or climbing onto monsters and holding on to monsters? These rules should cover climbing up giants, leaping onto a dragon's back, or holding on a roc's leg as it flies away.