I have been on several projects similar to the one described and I would caution that before diving into the build-vs-buy decision, I think you should re-evaluate and see if you're solving the right problem. At this point, having spent millions of dollars investing in your ERP it's not feasible to swap it out but it seems that most of the pain lies in the applications that MANAGE the data, the Excel spreadsheets, Access db's, etc. I would suggest looking into a front-end PaaS cloud solution with good dev and integration API's upon which to quickly re-build these apps, streamlining and standardizing processes and workflows - the situation you've described is a common case for cloud migration. You may want to look at a platform which will vastly improve time to app (Gartner and IDC have studies ballparking how much quicker you may realize time to app with a good cloud platform), lower your TCO and the OPEX vs CAPEX model may be more palatable to your accountants when evaluating costs of rebuilding. Also, like another poster mentioned earlier, you should try and avoid going down the path of heavily customizing your ERP because it will be a pain to upgrade, like it isn't painful enough already. I'd suggest having a platform layer upon which to build your apps, interfacing with your ERP via an integration layer. Without knowing additional details, I would recommend looking into the Force.com platform (disclaimer: No, I don't work for the company but I've designed solutions on this platform to solve situations like what the OP describes, migrating macro-ridden excel sheets, databases, legacy apps like lotus notes, etc. etc. onto the platform while integrating with an Oracle/SAP back-end so I'm comfortable recommending it). It's a good platform to build upon, literally hands-free upgrades, with numerous dev integration API's that guarantee backwards-compatibility, better up-time than Google and various integration middleware solutions as well so you don't need to rewrite connectivity interfaces for all your apps if you ever decided to swap out Oracle ERP for say, SAP. And the language is fairly simple to develop in, simpler than say, Java so you could get your third-party SI to lay the groundwork and then maintain/build upon it internally or, depending on your internal IT team's capabilities, take the bulk of the work on yourselves. Just my 2c, seriously - consider a cloud-based solution to solve some of your most pressing needs.