I think the biggest thing to consider is that if you just, "Plan a cruise and whoever wants to go can go," you might be excluding people who you really want at your wedding. There are all kinds of reasons why someone might not be able to go on a cruise who would genuinely want to see you get married.
If you don't really care if some people you love have to miss your wedding because of the cruise format, then proceed with cruise planning. If you would be sad they can't be there, make sure your VIPs are able/available to attend before you plan.
A cruiseline wedding sounds like it wouldn't allow the bride and groom to go away on their own honeymoon afterwards. Also, this would require a commitment of the other guests for the length of the cruise. If you instead are talking about a wedding hosted on a yacht, that could be a great option. Maybe for some people, though, this might be more of a destination wedding, depending how close the body of water is. That would be fun but is not likely going to fit in our budget.
They do offer wedding packages. We want to buy a house next year and we also have 3 kids to take care of. That’s how we came up with the idea. A wedding for the amount of loved ones we have would be way way way out of our budget with no help from anyone. So we figured letting everyone know what cruise we are going on and if they really want to join us they will. And they can celebrate all week or however long we sail for with us.
Some cruises offer the ceremony the day of sail away. They allow (or did prior to covid) guests aboard for the ceremony & possibly small reception. The guests not sailing leave before muster drill. Then you and any guests sAiling with you enjoy your vacation. Also keep in mind that usually cruise weddings require you to be legally married before leaving on day 1. You can do this before or they’ll do a quick legal ceremony before boarding.
My aunt and uncle did one. The only people who went was their mutual friend(he walked my aunt down the aisle and was the best man for my uncle) and my mother (her MOH). It is defiantly a time, and can defiantly help you limit you guest list if you want to have a small intimate wedding.