Beleive there's an ex-SAC base in Arkansas where they'll happily reset the ILS to whatever angle you want - for a $$$$ fee. You don't need to any specific testing for up to 4.5 degrees (your basic ILS cert is meant to cover that) but most manufacturers will make sure that the FD control laws work correctly at the 4 degrees needed at, say, Marseilles, and that you can safely do a go around without too great a height loss. Based in the US, we use Van Nuys with its 3.9 as a stand-in.