Here's my suggestions using a virtual tag.
1. Copy and paste the following to label and formula box under Tags(1)> Define New Tags
FeatArtist=$Split($Split(<Title>,"(ft.",2),")",1)
Add the column to main panel and sort by it.
Select all the tracks that have a value in the field.
2. Go to Tools> Tagging Tools> Copy tag
Source: FeatArtist Target: Artist
Tick "smart copy" and "append source tag..." and put ";" in the box
Preview and Proceed.
3. Select all those tracks, open ASR preset pane, find "Generate Display Artist..." and run it.