Comment Keep ERP system customization to a minimum (Score 3, Insightful) 209
I've seen companies spend ludicrous sums on TYRING to fit square ERP pegs into their odd ball shaped hole of business processes. Keep customization to a minimum. If you can't find an ERP system out of the box to do what you need it to almost completely, then building external apps to do what you want is not a bad way to go provided you have in-house talent to manage it.
Also make sure the vendor approves of what you're doing in those external apps. You might find them blaming you for system problems and not provide support when you need it most. You can bet the odds of this go up if you outsource the dev work. It's nothing for them to blame a third party they don't have a business relationship with.
Just remember -- external tools are basically external modules that are only dependent on the underlying data. As long as the database schema doesn't change, system upgrades shouldn't have any impact on your external tools.