Bob Harland

If you tension your rig with the standing rigging and bottlescrew(s) then you would probably find a rope halyard adequate – provided your genoa/jib are kept tight to the forestay with piston hanks or clips.
4mm dyneema would be quite strong enough, though 5mm is less likely to cut into the hands – check the diametre of your existing halyard and try to match that.
I don’t think there is much benefit to be had in changing to wire on a wooden mast.