Seems like actual viking burials were....burials...I'm no expert but skimming a few Google search results makes it seem like the burning ship thing never really happened, or at least rarely. Most vikings were ritually buried with weapons, grave goods and sacrifices. The burning boat thing is a Hollywood invention from a Thor myth maybe? Anyway this is why it's not allowed in most places, you'd need a professional to administer it with as you say a specially constructed ship designed to fully create a body. Your family can't tie together some logs and burn you themselves. So we're right back to an expensive funeral industry, but now we get to witness the cremations outdoors so maybe a win.