Reading several ideas from across the forums, the following mix seems like it might appeal to a large number of people. No system will appeal to 100% of the user base, but this would remove the RNGesus aspect the large majority of us have come to despise.
Upon reaching a GC Tier, the 1st and then every "decade"/10th Command Crate you open will contain a bind-to-legacy "Gear Token" which can be redeemed for any piece of BiS (at that level) gear. This would require accumulating 131 levels past where the tier begins; however, you would be guaranteed to have all 14 slots populated with BiS after completing that grind with no duplicates. Any levels you grind above that could be used to gear alts. In the current system, this is pretty comparable to leveling from 181 to 310. If you make that grind, it seems reasonable that you'd have a full set.
Also, we probably only need three grades of gear within a tier. Adding the legendary gear seems to have complicated things and generated a lot of frustration (every time I get a 240 piece, I wish it was a 236 that could be upgraded). When you get a purple 240 now, it's not really BiS so it feels like a 2nd place ribbon, or a participation trophy.