I wouldn't do it. Nah.
First, in both VOOM and VOOT, there is NOTHING analog about the controls. The Twinsticks themselves are of the "clickedy" kind, both Saturn and DC variations.
Second, it'd probably be much better to use the standard PSX pad. D-Pad + the "action buttons" instead of two sticks. Personal opinion, but I think it'd control much better than moving the clumsy analog sticks around.
Either way, I think that, for most people, VOOT's fine with the pad. Nearly everyone has underrated the pad setups. If you don't enjoy VOOT enough already, buying (or making) the sticks won't magically make it better...
...Unless you REALLY want to be a good player. Especially for Dordray and Raiden.