I think this is a great idea, but I think it might have some unintended consequences. Would the PWAs open in their own window or as a separate window? PWAs are trying to train a new user model / expectation and if users start getting to them in browser tabs from NTP, it might work against us. I could easily see us making a new section for PWAs in NTP though. 

There's also the complication of what source the NTP is using:

 * the feed / content suggestions
 * suggestions based on Sync
 * Most Likely (local-only)

I made some changes a little while ago in Most Likely to add site engagement sorting aside the standard history-based scoring. Switching the NTP to use site engagement sorting exclusively would give installed PWAs an inherent bump automatically, but we could also look to adda hardcoded boost independent of whether engagement sorting is on.

We should probably chat to the Most Likely team regarding this.

I figure it should be less likely for an installed PWA to appear on the NTP because they would already have a shortcut installed in the OS.