Great post Cal.
I've always thought a PvP trait line would be nice for freeps as opposed to the bonuses you suggested because morale, power, resistances, crits, etc can all be aquired through gearing or specing certain ways. I played my Champ to R8 without ever playing creep. My goal was R9 but I decided the grind was not worth it to get (at the time) the only black horse in the game which was my only incentive. I then made the switch to creep - and I keep playing because of the incentives for each rank.
The following is an example of what I would want for possible traits in a Moors trait line which would also carry over to PvE zones - some of the incentives I'm listing are designed towards PvE to promote freeps to go to the moors.
Class - Champion
Rank 1 - no bonus
Rank 2 - no bonus
Rank 3 - either no bonus or Turbine can put their +10% infamy here
Rank 4 - +5% run speed (in combat and out) One of the most frustrating parts of playing a Champ is that getting in range to do anything can be difficult if sprint is down. I know some creep classes get movement speed buffs that I believe apply to in-combat also but I could be wrong.)
Rank 5 - +0.5 meters to the range of all strikes skills (this is to make our melee range comparable to a Reavers range)
Rank 6 - Similar to the creep corruptions, give Champs two options; Damage for Health, Health for Damage
Rank 7 - Hedge applies a 5s disarm to the target
Rank 8 - +15% chance for each attack of Feral Strikes to remove a corruption (obviously geared toward PvE)
Rank 9 - Morale requirement to use Fight On! is removed, now useable at full health.
Rank 10 - A strikes line critical hit now generates 1 Fervour
Rank 11 - Red Haze activates Flurry for 30s
Rank 12 - Battle Shout applies a 3s stun
Rank 13 - Continuous Blood Rage now has a reflective buff, on any damage reflect 20 damage OR 50% chance to reflect 20 damage if 100% would be OP (similar to a Reavers Blood of Fire)
Rank 14 -
Rank 15 - The -30% incoming healing modifier is removed for Fervour
I actually struggled to come up with enough traits to fill all the ranks (hence Rank 14 being empty and some of the bonuses not being all that appealing). Anyway, each trait is available to barter delving stones for as you rank (similar to creeps barter methods) but freeps are limited to slotting 4 at a time. I don't believe that 4 of these would make the Champ class OP but improve it for the moors and PvE alike. I know I would be playing my Champ in the moors again if incentives like these were available.
So, just my 2 cents. I'm sure we could each come up with bonuses we would like to see for specific classes. Happy hunting!