Simplified relationship table
In terms of simplicity, the relationship tables are pretty complex: over 10000 constraints on how elements can be connected. Their definition has been costly and error-prone in the past. Why not simplify their definition by using the abstract types been already defined in the metamodel?
Note that this would mainly support developers of ArchiMate itself as there would be less items to define, maintain, check and validate. I believe also language users would benefit as well as tool developers.