I can understand the sighs of expertise dice not being exclusive to fighters. One complaint about the 3E fighter has been its lack of something unique. Fighter-exclusive feats weren't interesting enough to count. I'm not fully bothered with other non-spellcasters having expertise dice. It would be the shtick of 5E. However, it would be nice for the fighter to be the best at using them. Larger die, greater amount to have, fastest access progression, more choices of what to do with them (unique maneuvers), etc. It has to be more significant than analogous getting more feats in 3E. There needs to be something to show the fighter is the absolute best in using expertise dice.