Connected Trench Systems between Allies?

[Renegade]

I think you are misunderstanding the concept of "link". I'm talking about the fact that, when you build a piece of wall, and then build another piece of wall in some distance, the two will be linked with additional wall pieces to form a complete line of wall.
You can achieve the exact same line of wall by building each segment of wall individually, one at a time, at a higher cost.

The same applies to trenches - this is purely about whether to trigger such "auto-lining" also when the previous trench segment is part of an ally's trench system, rather than your own. Just like with walls, you could easily achieve the exact same construct with the exact same features by just building your way there on your own. It'll just be a tiny bit more expensive (one piece more expensive, to be exact).

I'm not asking if I should introduce special logic to do weird inter-ally stuff. I'm just offering an option that'd save you one segment.
To put it in images, what I'm offering is that this
#..........#### automatically turns into
########## rather than you having to build
#........##### first.

That's all it is, really. If you manually build your trenches up to the ally, they'll be connected either way, if you don't want them linked, you can always just block the path or sell the parts.