Source code availability for Native visuals

As Power BI is having its native visuals, it would be great if we get code/extracted api for Native visuals. Few scenarios where it is important –

- Existing visuals need minor modifications as per the report requirements. If we have code for Native visuals, we can make necessary changes to it instead of creating from scratch. It will save the cost of development.
- Power BI visuals are updated with the new versions, however in few scenarios old version visuals fit to our requirements. Using code, we will be able to manage versions.

Thanks.