I am not familiar with your boat at all, but chainplates mounted inboard of the rail are usually bolted to bulkheads below decks. Glassing them in doesn''t seem like the normal method of attaching these highly stressed members to a boat.
Chainplates are mounted inboard to improve a boats ability to sail to windward. The tighter the sheeting angle the closer it can point toward the wind. Should you elect to move the chainplates outboard to the hull, you will probably detract from the boat''s abilty to sail to windward.
since the original chainplates have not failed it seems logical to replace them with the same size stock or possibly one size larger if it gives you a comfy feeling.