Because A-B has used the "PanelView" name for at least five different product families and dozens of models, the cardinal rule of PanelView questions is "What is the full part number" ?
The PanelView 300 Standard terminal cannot connect with anything but Allen-Bradley controllers*.
The PanelView 300 Component terminal is what I imagine you're using, since it does have embedded Kepware data servers.
None of the serial protocols appear to be IDEC-specific. Does the Microsmart support Modbus protocol ? That might be the common denominator between these products.
The FC4A indeed does not fully support the modbus protocol. I believe you can do something along these lines but I was told the UK distributor that it was not easy.
The FC5A Microsmart Pentra does support the Modbus protocol.