if I worked at WoTC (man would people hate me) and I wrote and got published 3 new feats.If everybody wants it, or believes they need it, or compare other things to it--then it's probably unbalanced.
1)Improved toughness: You gain 10(3d6) hp and 3d6HD you can spend per day like your normal HD
2)Spell Casting Dabbler: You pick up to your prof bonus spells from any list of spells and add them to your spells known and they always act as prepared, These spells can not be higher then 1 less then your highest spell slot.
3)Spellfire: You gain the detect magic and absorb element spells at will, along with eldritch blast cantrip. special any round that you have extra damage dice from absorb element you can change the eldritch blast damage type from force to the element type, if you do you can add them to 1 ray of damage as no action on a hit.
all three would be REAL hard to choose from... but all three are pretty unbalanced for a 4th level character