We study various modifications to the minimal models of gauge mediated
supersymmetry breaking. We argue that, under reasonable assumptions, the
structure of the messenger sector is rather restricted. We investigate the
effects of possible mixing between messenger and ordinary squark and slepton
fields and, in particular, violation of universality. We show that acceptable
values for the μ and B parameters can naturally arise from discrete,
possibly horizontal, symmetries. We claim that in models where the
supersymmetry breaking parameters A and B vanish at tree level, tanβ
could be large without fine tuning. We explain how the supersymmetric CP
problem is solved in such models.Comment: 22 pages, 1 Postscript figure included, uses harvmac, epsf. Two
references correcte