Ideally, it would be nice, but in practice, it is quite cumbersome to do.The TemplateContext.MemberRenamer can be changed at any time, and it would require to check this and rebuild a new set of builtin functions. Also builtin functions are cached (only created once) so that they don't generate a new one everytime with create a new template context.
That being said, It is true that a ScriptObject doesn't take as a parameter a template renamer, so it is making all ScriptObject that are using auto-import of methods not usable with a different renamer (as this is the case for builtin functions)

So at least a first step to improve this situation would be to allow to propagate a MemberRenamer at ScriptObject constructor time, to pass it the the Import call here:

https://github.com/lunet-io/scriban/blob/d00574d4e2858f31cbc3891b394f8c5fb0d00a92/src/Scriban/Runtime/ScriptObject.cs#L49

And then add a new BuiltinFunctions constructor that could take a MemberRenamer and propagate it to the internal constructors (without using the internal DefaultBuiltins cache)

PR welcome (don't have enough spare time to work on this)