Instead of planning layouts, as you stated in BPS, you will be creating input ready queries that will allow for specific key figures to be changeable. Please note that you will use RSPLAN and everything is via the web. When you create the query against a planning InfoCube you can your query will be plannable and within the planning tab in the query, you can choose if the data is plannable when it is opened or not:
In addition, you can call all your planning functions, that are created using BADI's, via buttons within the Web Application Designer, etc...
You can find more information on Integrated Planning here BW Integrated Planning - SAP NetWeaver Business Warehouse - SAP Library
Let me know if you have specific questions beyond this and I can help you answer them.