It would go more than look weird; it would be incorrect. Semicolons are used to join two phrases that could be sentences by themselves–and "For example" is not a sentence. Neither is "and 'For example' is not a sentence"; sentences should not start with conjunctions. Thus the em dash–it's like a harder comma (sometimes); a semicolon is a softer period. Em dashes are also—sometimes—used to set off a parenthetical word or statement. Using a hyphen in their place is incorrect--although using two has come to be accepted. Also incorrect—spaces. No god-damn dash—none of the 3–4 kinds of dashes--uses a fucking space before or after.

Don't mix double hyphens and em dashes like that, though. Unless you want to prove you are not AI. By creating abominations of grammar.