I have some wallet credits I got by re-booking my upcoming trip when prices went down. But since I have no definite plans for travel for the rest of the year, I was trying to figure out if there's any good ways of burning it on this upcoming trip.

Alaska seems to be clever and only allow this wallet credit to be used towards "base fares", which I guess would exclude using it on upgrading to premium economy since that's technically a seat reservation fee, or paying for lounge access. The credits aren't enough to pay for first class, maybe I could re-fare and upgrade with miles? They do seem to have opened up U space. Unforttunately I won't have elite status until after this trip concludes. Any options I'm missing?

I also believe that upgraded with miles tickets aren't eligible for lounge access, either?