You describe the conundrum well, on top of which there are discussions over limiting the Vampire transport ability which has similar effects on large WraithGuard formations. The simple answer is that you probably need to revise your strategy to fit these restrictions. This in turn becomes an exercise in placing objectives in sensible places to fit the strategic theme of your army.
Infantry formations on foot can contest the opposing blitz, but they have to start opposite it and must march at least once in the three turns, most likely twice or more if they have to deviate (to gain cover). However, they can contest T&H objectives much more easily, and can also fight whilst doing this. The standard tactic to oppose a slow (infantry) army is to spread the T&H objectives (often to each side of the table). So you need to anticipate this in the placement of your own T&H objectives.
You can also strengthen your strategy by having several themes; eg. if you replace your Blitz with the 'Gate, this means that your webway formation(s) can adopt a more defensive posture should all your SS be destroyed.
Equally it may just possibly be sensible to field three SS in two formations, allowing the potential to use the Eldar triple move to deploy the SS pair, and then have two formations enter the table. The other question is which formations to keep off-table, and what their tactical role should be.
One of the main dangers of the SS is over-commitment; it is very tempting to use this tactic early in the turn before the enemy destroy the SS, but doing this puts two or more formations in a location where they can be destroyed by the remaining enemy activations - so pick your target location wisely, preferably on one or other flank (near your T&H objectives . . .

). You may also want to consider a vampire or two to transport further support to the SS location, or have high speed formations that can be doubled / marched over.
These are the kind of considerations that impact the intended strategy of your army, which in turn need to be taken into account when building the army.