The simple way to get the same effect is to simply assign, from the edit menu, the ProPhoto RGB profile to the image. This is the same as exporting and saving the file w/o a profile then attaching ProPhoto RGB to it when opening. One further advantage is that saving as a jpeg invokes lossy compression and simply assigning ProPhoto doesn't lose info. It just causes it to be re-interpreted. It will change the tone curve to a gamma of 1.8 so you will see a general lightening as well as the substantially increased saturation.

You can then convert the image to any other colorspace if desired. For instance you might want to have the image in Adobe RGB which is a good match for most wide gamut monitors. Or just convert back to your original working space. This will retain the changes seen in assigning the ProPhoto profile but will remap the RGB values to the smaller colorspace. You can then place this image in another second layer. I don't think custom luts in a filter layer would provide as accurate a result.