Data Model Adapters
Exploiting an external repository ecosystem to hold adapters
If type systems had some official names (such as might be done in Maven, which include versioning), then even if type systems were not completely "published", (partial) conversions between type systems could be put up in these repositories and automatically reused by UIMA applications.
Contributors could be incented into a web-based eco-system intended to encourage reuse, perhaps along the lines of stackoverflow (merit points, etc).
Type and Field renaming. If one annotator called a feature "tokenLemma", and another one called a similar feature "lemma", this could be supported by having multiple getters and setters for the same underlying field in the Java class.
More complex adapters might include some custom things (that could be Java "wrappers" that give additional views of the same underlying data - thus avoiding the problem of duplicate data for the same idea).