[quote=@Dark Jack]
(I also privately wonder whether naming it "Vlad" would make sense in context. It makes sense to us because of Vlad the Impaler...
[/quote]

In the Bloodborne universe this would make no lick of sense as Vlad, nor any person of similar relations, seem to have exist. They do impale and put people on pikes, sure. Yet No one man was ever named responsibly, so we would have no name to really tie it to. So Vlad would just be a standing name as a real name can be made for it later. As in Bloodborne very few weapons have been named. It being named I could think of as it would probably be the only one of its kind and it would more likely a decorative piece or a sign of the growth of Yharnam. I could see it being set up by the church for this express purpose. Or just some bat shit crazy Godo level blacksmith and a Guts level hunter came together to fight beasts in the most batshit but, if I do say so myself, badass way possible.

If a name was designated easily it could just be called, Pile Driver. Yet there is no oomph to it, so I dislike the name immensely. If it was mounted in a high place it could be called something dealing with its positioning over a function, God's eye, Sun's Scorn, and the such. Yet I don't feel they fit well enough. If it had a schematic with it from the Powder Kegs, then it makes sense if it is simple as the don't make names that are over complicated, so Pike Launcher could work but it is tactless to say the least. So I have came up with a name I feel would work.  

V.L.A.D

Violent
Long-distant
Agonizing 
Death

(This is a joke, but I find it hard to think of a name for it at the moment)

Also if a Powder Keg did make this, then I can only think the piles are each hollowed out a bit and filled with an explosive device that goes off after a certain time upon impact. Like the god damn arsonists they are. So then they would be able to pin the larger beasts then when exploded it would wound the beast further by cauterizing the fuck off size hole and sending shrapnel into it and shredding it further. (This is best result, worst result is a shit ton of collateral damage)

Then lets not get started with the fact of you will be firing from a long distance if we scale it to that size and launch that fucker. You can either:
A- Hit the Beast.
B- Wiff and hit the ground.
C- Wiff and hit a building.
D- Wiff and hit a fellow Hunter.
420- You jump off of the tallest tower with this thing, and hit the greatest YY ladder scope and pin 4 different beasts together to make the greatest Hunter-kebab. For all of your hunting needs. And look! It's on the go! Great for using to get a quick pick me up!

Edit:

Ok I just had an idea after reading it again up to the part that they are arsonists. What if the damn thing was on fire. Just hyucked a human sized stake that was burning them from the inside. Like the true arsonists they are.