The image is missing the third Dynamite link?
The image is adjusted from vanilla; I can't run at the moment (for a few more days) because my graphics card is busted.
Adding an upward link creates a four-way crosslink scenario
Right, but thats not that big a deal IMO.
It would be easy enough to have the vertical line bow out slightly rightwards when it crosses the horizontal line, to make it clearer that its crossing "over" the horizontal line.
Rifling would have to link to steam power
If you just added a link from rifling to steam power, that would also solve the problem, since steam power is required for replaceable parts.
What do yall see as the main balance concern with current military unit paths, if it could be put it in a sentence?
I think its that there is too much ability to ignore large parts of the tech tree in a way that is seriously disruptive to a sense of immersion.
It just feels massively wrong that I could have ww2 infantry or mechanized infantry without having ever developed Rifling. It feels massively wrong that I can have rockets without ever having combustion. Its bizarre that I can have battleships and rocket artillery without having ever developed 19th century artillery.
The problem is compounded by the fact that tech cost increases for each tier are relatively minor, so for example an extra modern era tech costs less than 2 industrial era techs. So I can advance further in late 20th century technologies without having a 19th century foundation. Its one thing to be able to ignore older techs if doing so doesn't really save you more than a couple of turns, its another thing when ignoring key older techs saves you half a modern tech.
However, my own preference is to slow down late-stage upper-tree progress, and this would help.
Yes, probably. If the gain from skipping those early techs is relatively smaller, then there is less incentive to do so.
In terms of unit balance, I think the main balance issues are still that some strategic resource units are not powerful enough, that naval balance is off, and that air units are weak.