Maintenance Planner can be integrated if you are using Solution Manager 7.1, the traditional Maintenance optimizer is going to be replaced by Maintenance Planner.
Besides this if you are using Solution Manager 7.1, you can still integrate to Maintenance Planner, since SAP is providing such feasibility, i think it shouldn't be a constraint to integrate Maintenance Planner into your existing Solution Manager 7.1. The LMDB still has to be updated though, as it sends the managed system information to the SAP Portal and Maintenance Planner retries this information and pushes the XML to our download directory. All you have to do is update to the SAP portal from the LMDB screen.
With MP, there are also other advantages, pool you systems on MP and have one XML stack file, no need to keep change the SIDs of the XML file from the Solution manager using the transitional report RPT_MOPZ_COPY_STACK_XML.