Incidentally, I happen to have a build around most of this ideas. Everyone here kinda inspired me for this. So...
Half Elf
Alternate Racial Traits: Fey Thoughts (Use Magic Device, Appraise)
Unchained Monk (Sensei, Scaled Fist), Oracle (Seeker), Cavalier (Daring Champion), Battle Herald
Progression: Monk 1, Oracle 1, Cavalier 4, Battle Herald 6
Abilities (20p/buy)
S10 D10 C14 I14 W10 C16+2
1- Advice, Draconic Might, Stunning fist, Unarmed strike, Dragon Style, Noble Scion of War, Skill Focus (Perception)
2- Mystery (Lore), Oracle’s Curse (Legalistic), Tinkering, Orisons, Revelation (Sidestep Secret)
3- Challenge 1/day, Champion's Finesse, Order of the Dragon, Tactician (Outflank), Divine Fighting Technique (Way of the Shooting Star)
4- Aid Allies, +1 Cha
5- Nimble +1, Piranha Strike
6- Challenge 2/day, Panache, Deeds (Dodging Panache, Precise Strike, Swashbuckler Initiative)
7- Inspiring command +1 (Shake It Off), Improved Leadership, Voice of Authority, Lingering Performance
8- Easy march, +1 Cha
9- 2nd inspiring command (Sound the Charge), Deadly Aim
10- Inspiring Command +2, Inspire greatness
11- 3rd inspiring command (Keep Your Heads), Banner, Steadfast Personality
12- Teamwork feat (Swap Places), +1 Cha
Thinks to note:
I'm not quite sure if unchained monk could take the sensei archetype. If not, change with normal monk.
Second, having draconic might let you sustitute Wis for Cha for most of the Monk stuff (mainly for the bonus to AC), but, having also the Revelation Sidestep Secret to change Dex for Cha again, I don't know if there is any FAQ or ruling that disqualifies this possibility because this way you are getting Cha x2 to your AC (although from diferent base stats)
Havind said that, this is a martial build and more or less thematic. His role should be buff, dps, party-face. You can also play Rogue sustitute as a Trap defuser thanks to Tinkering.
By third level you add your Cha to Initiative, AC (x2), Attack and Damage (as long as you use a Star Knife)
At low levels, you are not buffing much with your Sensei's Advice, but this will pay off later when you get to the Battle Herald.
You can actually pack quite some damage: Cha+Piranha Strike+Precise Strike+Advice.
Skill wise he has almost all the skills of the game as class and 6sp/level, not bad.
His first order of business would be to grab wands of mage armor and shield as soon as possible. Later, a Returning Star Knife and Deadly Aim should open range options (not great, but still competent)
With the Herald features and the boost to Inspire Courage you will start to pack some nice bonuses to your allies.
All in all, it may lack magic, but has great AC, great attack, nice buffs and saves, and lots of skills.