It would be nice to have more control on the sizing and position of patterns in a patterned/semy field.

Ideally "t1": "barry-argent-gules-small" could be replaced by something like "field": {"pattern": "barry", "t1": "argent", "t2": "gules", "size": 0.8, "x": 0, "y": 0}.

The COA string would become quite verbose, though, especially if "t1": "azure" gets changed to "field": {"t1": "azure"} for consistency reasons (and the same would apply for patterned charges and ordinaries). Also, it would break all existing links.

Backward-compatible alternatives could be to use something like "t1": "barry-argent-gules-0.8|0|0" or "t1": "barry-argent-gules", "pattern": {"size": 0.8, "x": 0, "y": 0}, but I find this quite ugly.