When Square-Enix first introduced the idea of Set Bonuses during the Treasures of Aht Urhgan expansion, I kind of liked it, but I wish they'd have gone back and retro-fitted some of the older gear with these bonuses. By the time we get some Artifact or Relic armor now, for example, we could already have other pieces of armor for those slots that are better. There isn't really anything motivating us to equip this gear. Now with the introduction of Empyrean armor, we don't see set bonuses until the +2 versions and since, as of right now, there aren't +2 versions of Artifact or Relic armor, at least in those cases we could put Set bonuses onto the +2 versions of the gear. Abjuration gear takes a bit of effort to get, so perhaps both NQ and HQ versions of this gear could be given these bonuses. I don't want to go into too many details, but for fun, I thought I'd post my ideas for Artifact and Relic gear bonuses. Just a disclaimer: My 3 main jobs are PLD, THF, and PUP. Several jobs I've only really observed others playing, so I'm just messing around on those. I have WAR and NIN at Lv45 and 48 respectively

WAR
Artifact: Augments "Aggressor" (Accuracy bonus +5 for each additional piece over 2 equipped)
Relic: Enhances "Savagery" effect (+10 TP Bonus for the WAR and +5 TP Bonus for allies affected by Warcry for each additional piece over 2 equipped - grants the bonuses even if Savagery isn't merited, but boosts beyond the cap if merited to Lv. 5)

MNK
Artifact: HP Bonus (HP+10% for first 2 pieces and an additional 2% for each additional piece)
Relic: Enhances "Invigorate" effect (grants Lv 1 merit boost for first 2 pieces or +1 level boost - can go beyond Lv 5 - effect and 1 extra level boost for each additional piece equipped)

WHM
Artifact: Enhances Cure Potency (+5% for first 2 pieces and an extra +2% for each additional piece)
Relic: Augments Cure spells (Turns Cure into Curaga, but enmity gain is as if you only used Cure. Curaga affects alliance members and pets. Need full set for this bonus)

BLM
Artifact: Magic Atk. Bonus (+5 for first 2 pieces and +2 for each additional piece)
Relic: Augments "Manafont" (For every spell cast while under the effect of Manafont, spells become uninterruptable by any means - Silence, Stun, movement, etc. Requires full set and gear must remain on for the duration of Manafont to apply)

RDM
Artifact: Enhances Enfeebling Magic (Magic Accuracy +5 for enfeebling spells for first 2 pieces and +2 for each additional piece)
Relic: Augments "Fast Cast" (Enhances the recast reduction of spells by an extra -5% for first 2 pieces and -2% for each additional piece)

THF
Artifact: Enhances "Steal" effect (Steal +2 for first 2 pieces and +1 for each additional piece)
Relic: Augments "Steal" (Grants the dispel bonus from Aura Steal even upon a successful steal and even if you don't have Aura Steal merited. If you have it merited, each piece equipped of 2 or more grants +1 to the effect. SO, you could steal an item AND Aura Steal a buff)

PLD
Artifact: Reduces damage taken (-4% for the first 2 pieces and an additional -2% for each additional piece)
Relic: Augments "Invincible" (For the duration of Invincible, all magic damage will be reduced by 50%. Requires full set)

DRK
Artifact: Enhances "Last Resort" effect (Increases attack by an additional 2% for first 2 pieces and 2% for each additional piece, but does not increase defense down effect)
Relic: Augments "Blood Weapon" (Requires full set. Instead of damage drained being equal to damage dealt, damage drained is x1.5 damage dealt)

BST
Artifact: Enhances "Charm" effect (Charm +2 for first 2 pieces then an additional +1 for each additional piece)
Relic: Enhances "Beast Affinity" effect (not 100% sure how this would work with merits, but you get the idea here)

BRD
Artifact: Reduces song spellcasting time (-5% for first 2 pieces and -2% extra for each additional piece)
Relic: Augments songs (requires full set bonus, but depending on song level and elemental alignment, targets affected by songs are given a stat bonus. Knights Minne I, for example, gives VIT+3 while Knights Minne IV gives VIT+12)

RNG
Artifact: Enhances "Rapid Shot" effect (Rapid Shot activation +5% for first 2 pieces and +2% for each additional piece)
Relic: Augments "Eagle Eye Shot" (Makes the accuracy of EES 100% - it ignores shadows even. Increases damage multiplier to x6.00)

SAM
Artifact: Enhances "Store TP" effect (Store TP+5 for first 2 pieces and +5 for each additional piece)
Relic: Enhances "Store TP" effect Zanshin: Enhances "Store TP" effect (Store TP+10 for first 2 pieces and +5 for each additional piece. Zanshin attacks: Store TP+20 for first 2 pieces and +5 for each additional piece)

NIN
Artifact: Evasion Bonus (Evasion+10 for first 2 pieces and +5 for each additional piece)
Relic: Utsusemi: Occasionally grants bonus shadows (Activation rate for first 2 pieces is 5% and +1% for each additional piece. Number of bonus shadows varies from 1 to 2)

DRG
Artifact: Enhances "Conserve TP" effect (Conserve TP activation +5% for first 2 pieces and +2% for each additional piece)
Relic: Wyvern Occasionally is affected by positive spells (Activation rate is 5% for first 2 pieces and +2% for each additional piece. If a WHM casts Cure IV on you and it triggers, Cure IV is also cast upon your Wyvern. If a BLU uses Diamondhide and it triggers, Diamondhide hits your Wyvern as well)

SMN
Artifact: Reduces Blood Pact ability delay (Reduction is -2 for first 2 pieces and -2 for each additional piece)
Relic: Enhances "Avatar's Favor" effect (Requires full set. Avatar's Favor effects enhanced by 25%.)

BLU
Artifact: Increases "Blue Magic Points" (+2 for the first 2 pieces and +2 for each additional piece)
Relic: Augments "Azure Lore" (While under the effect of Azure Lore, gain access to all the BLU spells you have learned whether they are equipped or not)

COR
Artifact: Enhances "Magic Atk. Bonus" (MAB+5 for first 2 pieces and +2 for each additional piece)
Relic: Enhances "Winning Streak" effect (+1 level for each piece 2 or more - same as the merited bonuses above)

PUP
Artifact: Enhances "Maneuver" effects (an extra +1 to each stat for each piece 2 or more)
Relic: Suppresses "Overload" effect (Requires full set. Suppression effect is about 50% that of Kenkonken)

DNC
Artifact: Enhances Waltz Potency (+5% for first 2 pieces and +2% for each additional piece)
Relic: Enhances "Store TP" effect (+5 for first 2 pieces and +2 for each additional piece)

SCH
Artifact: MP Bonus (MP+50 for first 2 pieces and +25 for each additional piece)
Relic: Augments "Arts" (Full set required. Under Light Arts, Cure Potency +15% and Auto Regen effect of 5 HP/tick. Under Dark Arts, MAB+15 and Auto Refresh of 2 MP/tick)