Getting high torque before the turbo boosts –
1. Put in a supercharger The sc could be bypassed when the turbo comes on. It has been done before but would not be cheap.
2. The Subie 3L motor as in the Liberty is not the obvious answer, it is not a torque monster low down.
3. One solution would be to speed up your gear changes, or better, always be in the correct gear, not as easy as it sounds.
4. In the B4, Subaru tried a fast spool turbo coupled with a power band turbo. Many people think the small performance gain does not justify the cost and complexity.