I like this idea, a bridge (like the one in LGW) would make it much easier to get to the NSC and would also probably reduce the congestion on the tarmac (not sure if the latter problem actually exists).
Given that this is HK, rest assured they will fit that bridge with plenty of food/shopping outlets to recover the investment quicker. Just look how many outlets does the MTR manage to fit in the corridors of some busy stations.