Not entirely sure what you are trying to do, because set analysis cannot be used in the script, although you might be able to generate same results using if statements.
I would say that to be safe don't remove your front end expression, and create a new set of fields (as required) to try the replicate the result of the complex expression. Once you get the same output from the two methods, you can think of removing the complex expression.
I shall swerve your question and not answer it per se.
I believe the most important thing is the data model, and this can only be improved within the back end script as that is what creates it. Often workarounds for a poor data model can be frigged in the front end with, dare I say it, horrendous front end expressions and abuse of facilities like Alternate States. Some of these frigs can be really technically brilliant, but nevertheless will always be frigs to alleviate the symptoms of a poor data model.
My ethos has always been that bad symptoms should not be 'treated', but the underlying causes should be eliminated.
Set Analysis and Alternate States are both superb front end tools, so don't be adverse to using them, I certainly use them extensively. Just never lose sight of the fact that the front end is always 100% reliant on it's back end data model.