Inventory location is one of many, many problems our ERP system is tasked with. And we've looked at a lot of software packages over the years, both proprietary and open. In terms of open software the options are actually pretty limited and have the potential to introduce more problems with integration and customization than they would purport to solve by bringing in new suites of features. What is less limited and truly abundant are examples of other companies in our same position that went full-bore into an off-the-shelf solution and ended up severely disrupting their business operations and aborting transitions.
If nothing else, it's probably time we give OpenERP another look just to get an idea of how problems are being handled there. Pointers to useful reading would be welcome, if you've got any.
The best introduction is probably Integrate You Logistic Processes with OpenERP, a free ebook written by OpenERP S.A. themselves[1]. It's slightly outdated, since it was published in 2011 and meanwhile version 7.0 has been released, but the changes to the stock area where limited (except for the UI).
We have a demo instance for version 7.0 [2], but it's in Portuguese (though you can change the language). OpenERP S.A. offers a free trial.