The answer to this could vary depending on the school of International Relations to which the answerer belongs.
Realists would say that no biological weapons convention or any other such treaty could possibly increase security to any appreciable degree. This is because any state that wished to could simply break the rules. The convention would not stop them. The only thing that could stop them would be actions on the part of other, stronger, states.
Liberals/idealists might argue that such a convention would be worth it. They might argue that a more intrusive convention would put more pressure on various states to the point that some states would be persuaded that it would not be worth it to abrogate the terms of the convention. In this view, the more intrusive convention could actually be worthwhile.
The answer to this, then, depends on one's view of the efficacy of treaties in general.