Beyond the do-it-yourself realm, several companies in north america can swap in other Subaru motors and transmission, including nearly any combination of USDM or JDM turbo WRX or STi motors and 5- and 6-speed transmissions, some including the DCCD features.
In rough estimates, for 1/3 of the price of a new STI, you can have equivalent performance in your car.
On a tighter budget, make friends with RS owners (who will inevitably upgrade their cars) and watch for their take-off parts. Perhaps up to a whole 2.5L motor + 5-speed trans. (My opinion, though, if you're going to bother swapping the motor, just get a WRX motor or better put in.)
Like Ray said, the 2.2L motor is rather anemic, and there's not much you can do about it if you keep it. You can upgrade the suspension and have a very fun to drive, but not very fast car.
Just some ideas to throw around.
(If someone handed me a '99 L today, it would
SO be getting an full STI drivetrain swap.
)