If you can get away with uniformly scaling the skeleton, you could group the skeleton under a transform node and scale that. (Be sure not to freeze the transformations of the group node after scaling)
If you need to non-proportionately scale the character, you could attempt grouping the specific limbs (or parts of limbs) under transform nodes, and scaling those.
(This is a big hack BTW - but perhaps it will be enough for you to achieve your goal)