Hola Mark

The "yo que..." structure doesn't really work for when the subject is a different one to "I", so, for example to say "If you were me, what would you do?" you can't say "Tú que yo ¿qué harías?". For this you'd need the more literal "Si tú fueras yo, ¿qué harías?" or also "Si tú estuvieras en mi lugar, ¿qué harías?". The same goes for "If he were you...".

Saludos