1) ILNumerics targets Winforms only. But you may try to use a WPF WindowsFormsHost container? I don't have any experience with it and do not expect an improvement for your situation though.
2) The way ILNumerics is checking DesignMode right now: if the executing assembly (ILNumerics.dll) is not in the list of references of the entry assembly (LinqPad), DesignMode is considered. Therefore, I can see 2 "tricks":
- Make LinqPad depend on ILNumerics. Probably not the best solution though.
- Patch ILNumerics: Alter the helper method refered to by Joe Albahari to return false instead.
The second "trick" may could lead us to a future solution. I don't know, if the "normal" DesignMode property does work in conjunction with LinqPad either? Maybe we could combine the existing method with a settings switch for all uncommon cases.