So you could potentially add this card to your hand AFTER you play a tactician, play it, draw a lab and then play another tactician if you draw it with the lab?
This is correct, though it's not as easy as it may seem to play two tacts in a single turn. You'd probably need a strong card drawing engine and some luck to find another tact organically (as you mentioned in your example). Or you'd just need to draw two out into your hand and then top deck one with mandarin or courtyard. But even that's tough because you'd have to draw enough cards to expose both tacts. So you'd need a thin deck or some added drawing power at a minimum.
Or if you're planning to play two tacts per turn operation would require 4 tacticians and at least one ghost town and at least one deck topper (courtyard/mandarin). So for that setup to be profitable, you'd need to have vault, secret chamber, or a lot of action +coin cards, since you'd be discarding your whole deck with the tacts, anyway.
So while ghost town could make for a very powerful engine, it would take a lot of extra setting up than your standard single tact or double tact strategies. I would think that the most viable way it'd play out is as a hybrid of sorts, where you buy two or three tacts and plan to usually only play one per turn, but occasionally find a way to get a second.
Either way, as rinkworks said, it's probably more fun to allow this rare interaction than it is to write difficult language to try to make it impossible. The bottom line is that Ghost Town adds for a lot of interesting possibilities, and things to take into account that will keep us on our toes every time it comes up.