First of all, do not make your own syntax in yaml, this will never work, only thing that are show on wiki will work.
Second if I understand correctly you "have cake and eat cake", this mean same research can give you somting and do not give same thing if used in different context. As engine developer I can answer that situation like this should be never permitted because will make only mess in code and make bugs and corner cases.
For your problem, one solution is simply split autopsy to two parts, one that give info about alien and another about plastics.
Like:
STR_DEEP_ONE_AUTOPSY
STR_DEEP_ONE_AUTOPSY_INFO
Medic give only STR_DEEP_ONE_AUTOPSY_INFO that do not grant plastic.
STR_DEEP_ONE_AUTOPSY give for free STR_DEEP_ONE_AUTOPSY_INFO and unlock plastic.