For it to work smoothly there would also have to be a total somewhere in the Shipyard UI listing how much BP the shipyards are using to build components (so that you don't waste more industry than needed for the project).
It's up in the air how much assistance a shipyard could get maximum or how exactly it would apply to the Build Points.
I think these two points are the core of why I don't think this is a good idea. I feel like you're handwaving away a pretty big problem. How much of your industry would be getting spent on sending BP to the shipyard exactly? At what rate does each class of ship consume BP? Does that rate vary between classes? Probably. How will the industry BP go into ship construction so points aren't wasted?
I see two solutions to this problem raised by your suggestion:
1. Steve codes up a system that constantly calculates the right amount of BP to maximise shipyard construction in the next construction increment, without wasting BP for normal industry. Whatever's left goes to the industry queue. This would be easy for the player
if that player's industry is at the same population as the shipyard, which is not always the case.
But it's the worst from Steve's perspective, as this would probably require the most work to implement, of the ideas I've seen.
2. The player selects how many factories are diverted to shipyard support manually and has to adjust the amount to suit the current construction. Very micro heavy for the player, and still not all that simple for Steve, as it's still adding new systems to the game.
Given that Steve hasn't shown much interest in this feature, I don't see #1 happening. On the same grounds neither do I see #2 happening, but I wouldn't want #2 either, as that sounds like a lot of work as a player.
This reasoning is why I'm suggesting a way to quickly queue up components based on selecting a ship class. Doing it that way meets the following criteria:
1. Allows industry and shipyards to be dislocated, same as things are now.
2. Is only a slight addition to the existing systems and UI, minimising the work required by Steve to implement and increasing the chances it gets added in.
3. Is still only a few clicks to add all the components to the queue you need, and then that's it - no micromanagement (which is the the whole point after all).