To effectively improve on these issues and effectively optimize your SAP supply chain, I strongly believe that you'll have to focus on three things:
1. getting your planners to work with SAP functions instead of spreadsheets and 3rd party tools. This can be done through a series of workshops executed by some experienced SAP consultants who understand the full set of functionality that comes with SAP. In another blog post I suggest the use of a spider chart with specific activities to improve on the use of SAP functionality for materials planning.
2. getting closer to achieving your goals and targets with a focused set of KPIs and putting together an improvement program like I described in yet another blog post on performance targets and measurements.
3. to improve on sustainability you must get your planners, schedulers and buyers certified on the use of the new concepts learned and the functions and standard operating procedures defined. Such a certification program should be managed through an LMS (Learning Management System) so that you can pinpoint through the entire organization where you need to do more sessions and improve on the competence level.
You might argue that you don't need to do this as you'll achieve those goals and sustainability without using the full functionality in SAP (Excel and 3rd party work-arounds may give you the same degree of success?), but as per my experience that is simply not the case. You're kind of doomed to use as much of SAP as possible since you're company has taken the step of acquiring it. Working outside of SAP simply destroys integration, data quality, flow and efficiency. And if you think that a 'best-of-breed approach is the better choice then you should first convince your executives and IT to switch gear. But as long as your company's strategy is SAP, you're stuck.
But don't despair. Turns out that once you're finding out about all the neat and exciting functionality that often lies hidden under the surface, you'd be surprised what you can do with this phenomenal system that was developed over so many years with a real smart group of developers and experienced supply chain enthusiasts. All you have to do is to dive in and formulate a sound approach and the magic might just happen.