I would leave the gun alone unless there your needs/wants are very particular. If you have an exact configuration in mind go for it. Choose your smith choose your parts and do it but know going in that you will pay a lot more than an off the shelf configuration with an equivalent but not identical setup.
This is the reason so many people buy what I call production custom. Every manufacturer of 1911s offers features on a stock gun that you used to have to get a smith to do.
The SA mil spec is a good base gun but it will cost you almost what you paid for it to customize it. You have to ask is it worth it.
"Its a tool box... I don't care you put the tools in for the job that's all..." Sam from Ronin
The United States is a nation of laws: badly written and randomly enforced. -Frank Zappa
Without deviation from the norm, progress is not possible.-Frank Zappa