Would like to be able to include a block as part of a structure, but config it to transform into another block after a given time.

This would allow users to specify non-traditional, external fuel source blocks, or do things such as create an oil rig on a special oil-source block that would eventually be consumed, or create machines somewhat analagous to Reika's RotaryCraft bedrock-breaker.

I would suggest instead adding the ability to break or change blocks as an output for the machine. It'd be more flexible, IMO. You could also add it as an input.

Yes. Please. I second this.