Using \import would bring the local procedures into the current tiddler's scope...but everything in the current tiddler's scope is made global by $:/tags/Global, so separating the procedures into a separate tiddler wouldn't actually achieve anything in terms of avoiding pollution.

Most serious programming languages solve this problem in an elegant way, by automatically namespacing (basically, a formalized version of prefixing the names) the things you import. If you imported SomeTiddler's procedures, you would say SomeTiddler.procedurename rather than procedurename to access them. Unfortunately, TiddlyWiki doesn't currently offer this – maybe some day!