Earlier this year I had multiple LH segments on a 016 ticket. I upgraded one of the LH segments from Economy to Premium Economy (straight upgrade, no bidding) for like ~$300. Original fare class was L. It credited as N class (Discount Premium Economy), but I also got PQM and RDM as if it were a non-016 ticket (100%); furthermore PQD showed up as ineligible.

I think if for work I end up with a 016 ticket, I'll upgrade segments to Premium Economy to make my 016 tix act like it's not a 016 ticket and hopefully get PQP.

Disclaimer: I don't know how United would actually treat such a ticket/segment next year; YMMV. I would be very interested to have someone try it out and see what happens next year.