Move Cursor to a Specific Character?

Not a Pages power user, so I may be missing some nuance here, but why would

...followed by

...be "mighty slow and clunky"?

Anything else is going to depend on you visiting the body text and then every text box in turn, since the find and replace in Pages has neither AppleScript nor Shortcut support -- and that's before getting into how to find and change the text. Even if you've multiple searches to do, that's going to be way trickier than using KM to automate the built-in dialog.

Edit to add:

So here's an AppleScript to find'n'replace pairs of terms across the whole(?) of the front Pages document. It's working on a short document, but see this thread for problems you might stumble across.

set pairsList to {¬
	{"(", linefeed & linefeed & "("}, ¬
	{")", ")" & linefeed} ¬
		}

tell application "Pages"
	tell document 1
		set thePages to a reference to every page
		repeat with eachPage in thePages
			tell body text of eachPage
				repeat with eachPair in pairsList
					set (every character where it is (contents of first item of eachPair)) to (contents of second item of eachPair)
				end repeat
			end tell
		end repeat
		set textItems to every text item
		repeat with eachTextItem in textItems
			tell object text of eachTextItem
				repeat with eachPair in pairsList
					set (every character where it is (contents of first item of eachPair)) to (contents of second item of eachPair)
				end repeat
			end tell
		end repeat
	end tell
end tell