Yes, antennas may be 'mixed' together, this is a typical application for
point to multi-point Mesh. The link budget of the Mesh link(s) should
be calculated and the antenna patterns considered as per normal
best-practices engineering for all RF deployments.
FYI, a given Mesh link may be monitored for Link Quality from the Aruba
Controller under Monitoring/Mesh Nodes/Topology. There you will be
able to view the Link Quality metric of the mesh link in real-time.