anti-casa, the obvious is sometimes what governs the rules. Class C is set up for IFR so they do not particularly want VFR or IFR below LSALT/MSA/MVA which can become unpredictable if conditions deteriorate. The current rules for VMC and special VFR give the controller choice to reject VFR flights when conditions are marginal and workload high. As far as wanting to proceed in VMC below LSALT why not just accept the instrument departure procedure and then request the visual level once airborne (If in VMC). The AIP rules only govern the assigning of or request of a visual departure before take-off, once inflight you must only maintain VMC for the level chosen.