One immediate issue is the notorious 28% chance of retaliation per intercept - I did very little interception in my full run because of that. 3-mission of course denies that, so you'll have to roll the dice on keeping the scouts away - and you don't get Transmission Resolvers until you go to an Artefact Site. The next issue is how the hell you're going to get the colony done with no drills (Calcinites are mutually exclusive with all of the three things that force three missions prior to T'Leth), no Ion Armour (that requires an IBA, which you're getting from the colony) and likely no psi (you can screen, yeah, but you've got no missions to train up your psi-guys). On my full run I got no Calcinites in the entire game, and ended up using psi in order to get past the colony mission; without that we're looking at a real ball-buster.
I suppose the alternative is to just hope for a Lobbie Dreadnought, identified via Transmission Resolver (gotten after the Artefact Site). Fighting a Lobbie Dreadnought with sonics and plastic is not fun, but compared to an actual colony it's a walk in the park.