This would be a nice thing to be covered in the FAQs. Beside this, in our group we play that some part have to be in 5 cm but not the entire base.

An FAQ for this sort of thing is always going to be problematic.
There are some groups that play a certain way and there are other groups that play differently.
Neither may be inclined to change there interpretation and that's fair enough.

The 5 minute warm-up conversation is almost always going to be the best way to make sure players are on the same page before the game starts.
If it's at a tournament, the tournament organiser can have final say.

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I think the chance of planetfalling an aircraft and disembarking two formations either side of a titan is pretty much zero. For a start, you have to pre-plot the coordinates. Then, the aircraft scatter. And then, you can only move them 5cm - even if maxing the distance, strip bases would still only be 9cm, so the aircraft would have to be right next to the titan's ZoC to draw a LoS from one formation to the other.

If my opponent wanted to bet his strategy on exploiting this rule, I don't think I would mind.

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Agreed Kyrt.

The only way you are going to get crossfire is with a completely different formation on the opposite side of the target. You might just about engineer this by moving something into position before the planetfall takes place. However this requires the assistance of your opponent and a great deal of luck.

Hardly the basis of a sound strategy. As Napoleon would say "it is *rude* to interrupt your opponent when he is making a mistake".