First of all a small disclaimer, since i am not that familiar with the capabilities of OXCE+ i might make some wrong assumptions.
Been thinking about the whole connectivity issue and there's an aspect that I failed to consider with the connectivity, namely how it limits facility building - to build in a row from A to C, you need to build first facility A, then B, then C.
This is basically a road bump so that you can't build all 36 slots at the same time, and it's a necessary one for a number of reasons - as Solarius said, connectivity would be worth pursuing but only as a part of larger redesign, which I'm not interested at this point.
I was under the impression OXCE+ allows replacing buildings, now if i assume the original tile stays available during the build phase of replacing why not use the following approach:
* When building a new base start with tiles that are of a building type that allows omnidirectional connectivity.
- Either as default tile upon base construction or a building type with 0-day construction (like the access lift).
- For instance "sewers" , "caves" or plain "ground level fields" (last one will require each facility to have some sort of access to the ground level, otherwise you risk having "disconnected" tiles during construction).
* Now the player can replace/upgrade those tiles as desired
* Optional: Let the player remove those tiles that are not needed for connectivity so it can still have "choke point" defensive base layout (although this might need a connectivity check when removing).
Could this work?
...
However, there are two separate issues that would need to be addressed:
1) limiting the damage to the single building that is hit (and not losing any connected ones)
2) ensuring that friendly units can reach any facility that has become isolated because of the missile strike. Tech-Comm base terrain is designed that it solves the 2nd issue (with a ground level) but on vanilla it will require some change.
Since it is sometimes hard to gets ones ideas clear using written text let's try to elaborate a bit.
1) I believe it is not so much part of the base building concept but a functionality of the missile strike routine. Hence the proposal to "convert" the targeted tile to the "rubble building", instead of removing it.
2) If using the "convert" routine this should not be a problem under the condition the mod provides a "rubble" facility with appropriate connectivity.
Hope i made myself a bit clear.