How about they just increase the stats of what current gems add? Like +7 or so for lv40+ items. It already scales up with the lvl of the item so it wouldn't be hard to implement. That way the normal gems are at least still a decent option compared to gems that can't even be obtained anymore.

I was honestly surprised when we got the new cap and saw that we still just got +6 stats with normal gems... Just like last cap.