We are using Excel Services to present BI reports on SharePoint 2013. We are quiet happy with the results, but need to customize the PivotTables and PivotCharts for our client to some extend. One requirement is function hiding: the end user should not have the option to choose a dimension to display for example. On the other hand, if it is required to choose between a number of different dimensions for the end user, then we have to offer exactly those allowed dimensions to the end user (in an option list).
So the customization is rather deep and I am not sure if Excel Services is the tool of choice for our purpose. However, if someone has customization tips then I would be happy to hear about it. I would also be grateful for tips recommending an alternative toolset for our aim.