Yep, the placement of such a chain pipe would be a mighty inconvenience, to say the least. As to the why behind it's being built that way, I'm uncertain.
Regarding your concern that the pipe's a major structural member
, my guess would be no. But barring an eyes on good look it's tough to say.
A lot of the answer to the question has to do with where the windlass
is mounted, & whether or not the deck
structure was designed to handle it's loads with, or without said pipe in place.
That said, might you contact the builder
& ask them? Also, can you get a local, quality, builder
or three to offer up opinions? Ditto on surveyors with engineering backgrounds.
Regardless of what any of the above may tell you in terms of it's current
necessity for being there, even if it is "needed", there are ways to do structural modifications to the deck
such that the pipe isn't required. And in saying that, I'm assuming that the windlass
is currently mounted in close proximity to the pipe at the moment.
Then the question becomes one of how much is it worth to you, as well as where will the new chain locker be? Also, as a test, before breaking out the tools, in order to make modifications. Try moving all of the chain which the locker contains, or might at maximum capacity, up to the forepeak. Assuming that that's where the new locker will be. And then take the boat out for a spin in various conditions.
Thus you'll get a feel for how the boat will/would handle if you move things around. As the weight of a few hundred feet of chain on a boat that size can significantly alter her handling - both underway, & on the hook.
One other option to perhaps consider, is, how much trouble might it be to have an angled or curved pipe shaped so that it leads the chain over to one side of the bunk, or it's head
? At least in that case, you more or less get a true double up forward. Though you'd need to factor in the structural implications again. In addition to possibly a new chain locker & it's attendant drainage.