If I had luggage to bring with me, I'd hire a car to Itami and fly from there. Generally, JL/NH are good with checking bags through on separate tickets and it just means less manhandling of bags on my own. I feel this is the most comfortable option.

Sending all checked bags ahead to HND is also an option if I'm looking to do some last minute shopping/dining on the way via trains. As others have said, you'd need to send the bags at least 2 days ahead of time. If looking to use this option, check with your hotel on the specifics of when you'd have to book the luggage delivery and when the bag drop deadline is, as it can vary property to property. Most hotels I've stayed at also provide a map showing where the pickup counter at the airport is.

I once made the mistake of bringing a checked bag with me onto the Yamanote around rush hour and I swore never to do that again.