Hi,
We may be misunderstanding your request. If so, we apologize.
There is an NXP tool by the name "S32 Flash Tool", which lets you flash your external device with the S32G set as serial boot. Is this similar to what you are looking for? The restrictions that may have is the available algorithms by default. You should be able to add new algorithms if required, but this is to be done by the developer.
This tool is available as a bundle under S32DS installation, and should be available under the following path:
"C:\nxp\S32DS.3.4\S32DS\tools\S32FlashTool\GUI"
Please, let us know.