[Answering an old post here, but since I dug it up looking for
a similar solution I figured I'd offer back my 2 cents.]

The above will likely work for a two-position monostable switch but
I doubt it will be reliable attempting a center-off configuration.
Reason being the hysteresis built into the toggle spring mechanism
is going to resist allowing the switch to rest in the center travel.
Even adding two opposing springs into the molded spring retainers,
you may get the outer switch rocker to center rest but the internal
contact is unlikely to be centered between opposing contacts
with sufficient stability to be reliable. Ask me how I know.

Alternatively I'd toss the entire power contact mechanism along
with the rocker spring. Two consumer-grade snap action push
switches fixed in the toggle base over the spring retainer holes
(springs themselves omitted here) will provide the low voltage
contacts. The only other consideration is restoring the spring
"lift" to the rocker switch center which can be accomplished
with a block of stiff foam (or better yet, a simple compression
spring). This restores the expected toggle "feel" to the operator.

The other possibility this approach allows is dispensing with
the brown contact sub-housing along with screw contacts.
Doing so reclaims a substantial unused volume which may
be useful if you need to add some circuitry "in there".

Of course this limited to low voltage circuit use. Even then
the NEC may cast an evil eye at this type of modification
although I haven't bothered to check.