This would be highly useful, especially in situations where you have peers in a dependency chain, but would require a fair bit of dependency management.
BCD depend on A
E depends on C and D
F depends on B and C
G depends on E and F
A would have to be built in isolation, but B, C, and D could be built simultaneously. E and/or F could be built, only with BOTH of their respective dependencies are done. One way would be to fork threads for each build. Each would know their dependencies and poll them until they receive a "yes, I'm done", then they could begin on their merry way.
A key problem with this, is that Maven assumes that all build artifacts go to the central repository, so relying on maven itself won't be a solution. Continuum would have to maintain more build state. This should be fine, since it already scoops up dependencies and displays them, but the point is that it would have to be a Continuum solution, not a maven solution. Also, if it were, and if dependencies for ant/shell build types could be added manually, as long as those dependencies were also in the current Continuum instance, then such a solution could work for any and all project types.