While I see non-leaping Michaels as being the best route to find the slam, you have to live with the choices your partner makes ahead of you.
Given that partner made a takeout double and you have two potential places to play. I think 5
, albeit almost certainly safe, does not give the full playing-strength of the hand, while retaining a modicum of safety if partner overbid. A direct bid of 4NT is called for to show two suits; pulling clubs to hearts, and probably raising either red suit to slam. I feel like the pull of 5
to hearts shows a mild red suit try, while if partner does not show clubs over 4NT, then we have the double red-suit fit, and I am willing to try the slam now.
A delayed 4NT (waiting for the reopening double) just seems weird. If it were natural, why not pass the second double? I think the best interpretation is a balanced no clear-choice sort of hand, throwing the decision back to partner.