i'm curious why you didn't go the direction of adding this functionality to CDK directly? i'd like to use some of the functionality in here like live lambda development, but i also don't want to take on converting my org's already built CDK extensions and deal with migrations.
We had to change the build process of Lambdas to support deploying a mock version of the function. And we need to add a new command that deployed the debug stack.
Here's how it works internally — https://docs.serverless-stack.com/live-lambda-development
Your existing CDK app should work with SST. The main difference is that SST deploys per stage (or environment). This allows you to do `sst start` that goes to one environment and `sst deploy --stage prod` that goes to another.