It doesn't seem to make much sense to port EX on top of CELL. It makes more sense to centralize pair processing code since it is used in LEAF, EX, CELL (and PF). 1. It seems that most code in EX can be auto-generated: it's really mostly wrappers. The beef is in LEAF anyway. 2. The PAIR processing code can be abstracted and possibly reused in LEAF for its linear / RC cells.