Expose sde version for Named ESRI sde connections so can be a parameter at runtime

A workaround would be to use arcpy to create a connection file in the workspace, I have done that a few times in Python Caller, then you would be able to use all the parameters there.

I doubt that it would be possible to specify from FME for an existing connection file, they live in the ESRI domain of things...

That might work on a small scale, but we would have to have over 100 sde connections for what we are doing,  and then you would also need to have the credentials someplace  in that that ArcPy script to create the SDE connections. which brings up security issues of having credentials in a script or in a FME Workspace, nether is very good.  

You can have credentials in Database connections, and then you read them out in python using  fmewebservices.FMENamedConnectionManager()

I think it might even be more of a good fit for you if you have 100 sde connections, so that you don’t have to manage them separately. The negative is that it takes a bit of time for arcpy to create the connection.

You could also cache them if the values don’t change often.

In a scripted parameter, pseudo-code:

• read selected db connection from another parameter
• read version identifier from another parameter
• Check if a .sde file exists that matches those exists in a cache folder
  • if yes, return that path
• If not, read out credentials/server from db connection
• Create new sde connection using arcpy and return that path