Looking for help on a "motivator" character

[Ailur]

Hi all, i have to make a new character for a running campaign.
I want to focus on the rp "motivational" aspect of that character, because the party in general is not roleplaying their characters lately, so i want to focus on giving them rp hooks...

I know that this is something that any class can do, but i'm not a great role-player either, so i'm searching for a class that kinda help that aspect of the game and isn't useless in combat (which is the preferred moment by the party..).. so i'm willing to play a underpowered class as long as it's optimized.

The party is composed by :

Barbarian warrior dungeoncrusher goliath
Dwarf crusader
Mystra Cleric/Warlock
Cleric Animal devotion
Druid

Wizard/rogue PNG
A new entry that i don't know what will play.

Sorry if the request is a bit vague, and thanks for the feedback :)

[Inevitability]

Bard. The party is filled with melee characters who will love getting a few extra d6 of damage on every attack. Not only that, you'll bring some much-needed skillmonkeying to your party.

[Grod_The_Giant]

Bard. The party is filled with melee characters who will love getting a few extra d6 of damage on every attack. Not only that, you'll bring some much-needed skillmonkeying to your party.
I'll second this. Bards are great support characters, especially for a melee-heavy group like this one looks to be. You also get to bring skills and arcane spells to the party, both of which look like they'd be useful.

(If you're unfamiliar with the d6's Inevitability is refrencing, a basic Inspire Courage primer:
Dragonfire Inspiration (Dragon Magic) converts the +x from IC to xd6 fire damage
Draconic Heritage (CArc) lets you change the damage type of Dragonfire Inspiration
The spell Inspirational Boost (CAdv/SpC) grants +1 Inspire Courage when cast
Badges of Valor (Magic Item Compendium) are cheap, and grant +1 Inspire Courage 3/day each.
The feat Song of the Heart (Eberron Campaign Setting) grants +1 Inspire Courage, and can be nabed as a bonus feat by swapping out Suggestion as per the same book.
The feat Words of Creation (Book of Exalted Deed) doubles your Inspire Courage boost, but deals you nonlethal damage.)

If you want something simpler, Marshal isn't terrible. You can grant a small bonus to everyone's combat ability, and a sizeable bonus to their (and your) skills. Take Motivate Strength, Motivate Charisma, and Motivate Dexterity in roughly that order. Str is good for combat, pairing nicely with a trip-based build and your Dungeoncrasher friend; Dex is nice for stealth and balance, and Cha lets everyone play the socialite game a little bit better.

[Inevitability]

Marshall is good as well, though I'd pick Motivate Dexterity a bit earlier. After all, it boosts initiative for your entire party, and going first is always good.

[Telonius]

I'd go with Bard just for the size of the party. Bard is a force multiplier, and the more allies you have the more of a difference it makes.