This is done by design though. Allowing a character to use all their elite specialization’s weapons, regardless of the specialization they have equipped, means that the number of combinations of weapons, utility skills, trait choices and equipment increases exponentially with each elite spec added. The same goes for allowing a character to use all their elite specialization’s utility skills, regardless of the specialization they have equipped. This exponential increase in options is the detrimental to balance and since the elite spec system was specifically implemented as an expandable feature, it makes sense that they build it to limit future problems.