There's a number of assumptions there, though; firstly whether it's possible to synch up jumps in such a way (the haste shown at the end of FS1 indicates it's no trivial matter to 'share' a jump corridor with another ship), secondly it's assuming there aren't things like mines or heavy defense emplacements we've not seen (admittedly, it is a fair assumption - you'd expect to see them, after all), thirdly it's assuming blockades only take place on one side (I believe there are a number of cbs in the main campaign that have the GTVA defending the node from the 'entry' side, presumably for the reason of preventing such an organized attack), fourthly it's possible (if not probable) that the NTF could bring to bear sufficient firepower by way of cruisers and corvettes (to support their bombers and destroyers), and fifthly the NTF would expect and defend against any such attack.
Also, a blockade would not necessarily need to destroy an attacker, but merely damage it in such a way as to force retreat - for example, removing those 2 destroyers would force the cruisers to withdraw due to lack of fighter cover. After all, I'd wager a blockade 'run' wouldn't just need to penetrate, but to destroy all opposition and secure the node - and do so whilst other enemy ships were reinforcing the blockade (I doubt any blockade would just be a single line).
You make good points, and I only just realized the difficulty of lining up ships in a corridor. Still, you can receive messages from Command in a subspace corridor, so ship-to-ship communications, including co-ordinates, should be able to cross whatever dimensions prevent the two from seeing or touching each other in subspace, if only by being routed through Command. In this way, you could enter formation without having to use tracking technology, which, by the way, may very well be easy and fast to use by now. The haste in FS1 came from the late discovery of the technology and the race to implement it.
The GTVA would quite obviously take this side of the node first, assuming it's not heavily defended. Thusly 2 (undamaged, which is a bit stretching it,) Orions, despite the huge expense, could very well take out whatever the NTF had on their side with ease, which could be Orions, it could be corvettes, it could be cruisers, anything. It isn't often we see 2 friendly Orions together at once (read: massive amounts of money). For example; Allied force jumps in, NTF is surprised and opens fire with, say, Orion, Aeolus cruiser, and Fenris cruiser. While Allied Orions vaporise NTD Reliance/Resistance/Revulsion, the NTD Triumphant/Tedious/Truant warps in to reinforce the blockade. The bombers, guided by the impenetrable armour that is Alpha 1, pound it and the cruisers. The Orions are moderately damaged, and are reinforced by the Aquitaine, Alpha 1 gets promoted, and the day is saved. Of course, there are many other ways this battle could go.
The NTF is a much smaller entity than the GTVA, and has nowhere near their resources. I doubt they would send an armada to fend off GTVA attack, not unless they were pushed back to their core systems, and even then, in FreeSpace, we never see a battle where capship after capship on both sides get pulverized and new ones taking their place. One side always retreats, even though one location in space provides no strategic advantage to another.