Flexi : this type would require alot of input from a tech game master, who would provide research items to the players dependant upon what they had already researched, but as players went in one direction, say to engines, then other sections would get restricted, while the ones they research most would open up further. Meaning that over time you wouldnt be able to research say missiles, but your engines tech could have many many extra paths to choose from.
Sorry but unless your scientists and engineers are certifiably retarded
, I don't see what getting phat engines has to do with locking missile technology, or in fact any other area. In fact, getting phat engines would most likely be beneficial
to your missile/rocket tech.
It seems pointless and arbitrary to go locking off areas just because you took one route instead of the other. It might not be very cost effective to go back and work on the other routes, but that's what tech trading and scientific powerhouse groups are for.
So yeah, I'm against locking off areas permanently. People have to make choices as it is, so don't arbitrarily penalize them. They can opt not to have anything to do with beams if they wish, but actually locking technology off is something I cannot support as a concept. It makes no real sense. Any justification for locking techs is already presented by the fact they're overspecializing to begin with.