Well I'll get the obvious thing out of the way first
Blood Moons are based on a real event. Irl we call them Lunar Eclipses, where the Earth's Shadow passes over the Moon, resulting in a red color, hence the name "Blood Moon".
Blood Moons aren't connected to the Crimson, for the record, not everything red/bloody or purple/vile relates to the Crimson or Corruption, for example, Night's Edge isn't a Corruption weapon, rather, a "Demon" weapon, as it shares similar colors to Dark Lance and Demon Scythe.
I don't have much more to say about this, I could definitely see interesting content being added, but then you'd have add some sort of way to get a Blood Moon in Corruption Worlds for Completionists Sake, and Solar Eclipses are also based on a real event... a Solar Eclipse, so I dunno, it could be interesting but seems overly tedious for adding what doesn't seem to be meaningful content, in my opinion, especially because Terraria actually sticking to real world events is well, cool, as the world acting like that is actually accurate and a "Shadow Moon" wouldn't make sense in a scientific way(I know Terraria has barely anything science related, but Blood Moons are Solar Eclipses are from real life and in another world would act the same way, it's impossible for it to act differently), as Blood Moons are indeed, just a real life phenomenon, breaking that seems counterintuitive.
Extremely sorry if this comes off too harsh or rude, I don't want to.