TBH, R2D2, that was a rhetorical question.
How could a pilot who is only a skill 9 (for example) due to his proximity to another pilot be able to pass on this skill (it isnt really HIS skill… its a buffer from luke)
When you think about it, it makes quite a lot of sense. Wingmen don't just support flight leaders; flight leaders actually lead their flights. We're talking pilots who train and work together to follow each other's leads. You have to think about how these abstract rules might reflect what pilots are actually doing when flying starfighters. Luke is getting a buff by following Wedge's lead not because Wedge is zapping him with some magic power, like casting a spell or using the Force. So Biggs should be able to take that same cue from Wedge by watching Luke. It's like a school of fish. So the chaining OP mentions could indeed make sense and like I said it's not really abusive: there is a cost associated with this benefit -- in order to chain, you've got to bunch up.
Now, I don't think you can actually do that because of the flow of "time" in the game. Which brings us to …
I would guess that the answer to the OP is that this cant be done. I would assume that when it refers to the pilot skill, this actually means the unmodified pilot skill as shown on the pilot card
But what's your support for that assumption? Why does it refer to the PS on the card instead of the PS as modified by Swarm Tactics?
many game systems I play use the modified skill/value/roll etc when refering back to something
I assume you meant "unmodified" there, else your point is contradictory. More importantly, we can't really deduce anything relevant to the rules of this game from the rules of other games. The answer has to be in the rules for X-Wing.
To me, this is not a question of house ruling. The rules as written cover the situation completely. Given that "at the start of the Combat Phase" cannot refer to something different for every pilot, Swarm Tactics would resolve on the part of every pilot simultaneously. That means that while Wedge is conferring his PS9 to Luke, Luke is conferring his PS8 to BIggs.