Change the location of source photo (from Raw to a DxO-processed DNG) in LR catalog?

"... so think of them is a different version of the original raw"

It's been processed. It's gone through DxO's RAW converter, been adjusted, and written as a DNG. IMHO, it's a different image.

"This way I would not have to import the dngs and copy the develop settings from raw to the newly imported dng version"

If you look at the metadata of the DNG, there are adjustments applied. The only ones that appear in LrC Develop are Noise and Sharpening are set to zero. So what does it mean to apply your changes to DxO's changes?

I posted my impressions of PureRAW here https://www.lightroomqueen.com/community/threads/dxo-pureraw-impressions.42773/

Being very curious, I tried this-

1) Using the DNG Converter program, I created a DNG 'copy' of a NEF file.

2) In LrC I converted the same NEF raw file to a DNG from the Menu: Library > Convert Photos to DNG.

3) In File Browser I replaced the LrC DNG file with the 'copy' DNG

4) A [Read metadata from file] changed the Preview thumbnail appearance.

So experiments show that ADOBE DNG files can be replaced, BUT, a DXO PureRaw DNG file may not, in fact, be a raw file. It may be TIF RGB data (or even a JPG file)  'wrapped' in the DNG file-type cloak. And again the answer will be "..you cannot replace them...."

Fun experimenting!!

If your originals were RAW, you cannot replace them with a DNG.