I'd like some to be gameplay changing. Maybe some that use all but 1 or 2 points to choose. Or had massive penalties. Like playing master of magic with no magic.
Necromancy -15 points to start with (more than you have to spend). So to pick it you have to give up all the good traits and pick 5 bad ones, like repulsive... it could be as unbalancing as you like in the end game if it made you relatively weak against rushes at the start. Or it could be free but cause war with all races, repulsive and prestige penalties (neutrality with other necromancers)
(Hydro)phobic skin - no (water) mana, 25% (water) resistance. more points to spend. (for the warlord type builds - hydrophobic/impermeable - water, fire retardant/inflammable -fire, unsoiled -earth, rubber -air)
Oblivious - can't see new resources on map outside your borders, gains 100% extraction rate to res of choice.
Keen eye - can see resources within the sovreigns line of sight 2 levels above current research. (large cost?)
Vampiric - must win a battle (feed) or perform a spell in town (feast on the tasty) every 5 turns. For every 5 turns missed the sov's attributes suffer. after 25 turns the sov's vampiric unveiling causes rebellion/unrest/diplomatic penalties. But no longer needs to be hidden. Gains bonuses for each kill from that point onwards. (say up to a limit based on essence)
Werewolf - the sov alternates between 2 forms, a high power, fast form with no magical spells or the spell casting but weaker form. The alternating could be every 15 turns. The sov could also become a greater werewolf or control the transformations with magic. Allowing transformation at will and the creation of lesser werewolves.
Turtle magic - understanding the strengths of protection and a shell you became magically shielded. It wasn't till afterwards that you realised that turtles aren't very dangerous. +50% defence (mundane and magical) and +30% HP bonus -75% attack power (physical and magical) bonus to diplomacy on trade, unable to threaten or demand.
Wild magic - each turn your mana income could be +/- 20% of normal, and your spell power fluctuates +/- 30%, allowing you to cast spells early and fast, or not at all. So too the power of each spell can vary, or can have strange consequences.
Attuned Wild mage - same as above but has greater attribute cost but you get to see in advance the spell effect (say it's highlighted in your spell book if you'd have a good trick effect) and able to see the next turns income and power. say +15% to - 25% income and +25% power -40% power as a further cost.
Isolationist - gains a % bonus for each turn inside your own territory, and a penalty each turn outside your territory. (bonus/penalty with diminishing returns, resets very quickly when you switch from inside to outside)
Explorer - opposite of the above, gains a bonus when in unclaimed territory
Warmonger - bonus when on the offensive
Also I'd like some actions that your sov can do that would take them out of action for a while. Unable to move but gives a bonus after the first 4 idle turns. For example:
Sage - able to join any library/alchemists to boost that cities production
Miner - as above with mines
Farmer/horticulturalist - food production
Creater/destroyer of life - spreads terrain type
etc. for mana production, training time, prestige, culture spread, building time
the only unique thing would be to use it for ritual magic. say after 5 turns in one spot you have the option of planting a totem to signify the rutials you've been doing. Do at least 3 of the same rituals and they mark out an area, each totem is another edge to the area. With each having some weakness (anyone can do a 'corrupt ritual' action for 5 turns to remove it) That way you could have your territory protected, buffed or any area that you can mark out.
It would make it a little different if you see someone hanging around your borders, they could be planting totems to gain an attack boost in your lands.