You call it acrobatics, I call it a mental exercise in figuring ouy why a thing might be the way it is instead of just declairing that the first thing I think of is the one and only possible truth. Technically, the ship has a module of unknown (but smallish) size that allows it to do its planetary landing stuff, the devs were just nice enough to make it a new dedicated slot. Of course, you've ignored that because it's not convenient.
The mass of the planetary flight module is not "unknown" it's ZERO, you know, like you'd expect from a piece of software. And I ignored it for that very reason plus the fact that every ship in the game has one for free and no sacrifice or tradeoff of any kind is needed to obtain one, kinda like it was a piece of
standardized software. Honestly how else would you expect them to model a piece of software in a ship-building system that only uses "modules" and nothing else?
The docking-computer should be no different, just a zero-mass software "module" that you buy, same as the planetary approach module. I actually agree with several people here that there should be some sort of tradeoff in order to have it but I strongly believe that the tradeoff should ALSO make some degree of
sense in addition to being good for gameplay. At the moment it makes no sense at all no matter how many credibility-straining mental contortions you go through to force it to. Some tradeoffs that make sense might include...
1/ Increase the cost of the docking computer dramatically, no module slots required, the trade off is the large amount of money you pay for the software.
2/ Have the ship's computer as a core module which starts at 'E' and can be upgraded. The higher rating the computer, the more programs (like the docking program) it can simultaneously run.
3/ Adopt something like Babelfisch's suggestion below.....
I'd like to have a system with submodules, let's say the sensors can have up to 4 submodules (or make it based on size) and we can install a docking computer in it. Other modules would be the various scanners.
I actually quite like this one because it creates a solid framework for future software package installation and incorporation where tradeoffs and decision making are still a necessary factor. Either way I think it should be possible to come up with good, fun gameplay without it ending up being ridiculously stupid or illogical. It just requires a little more careful thought than it has so far received.