Need advice on balancing out party

[The Human Diversion]

I'm going to be in a party of six playing Giantslayer, and 4 of the 6 players have already said what they want to play;

Aasimar Cleric of Iomedae
Hunter with big cat companion
Half-Orc Paladin of Shelyin
Kobold dex-based fighter

That leaves my fiance and I to choose how to fill out this group.

I've pondered playing an insane gnome gunslinger who uses a medium musket and thinks elaborate plans involving explosives are always the best option. My fiance was thinking something arcane, but is pretty open.

I'm not completely set on the gnome, but it seemed amusing to me.

Thoughts?

[My Self]

If you want to be a gnome, be a gnome. Party balance-wise, all you're really missing is a group buffer and an arcane caster. Maybe someone with range, too. An archer bard and/or a Wizard would fit in pretty nicely. If you can get a bard, then you'll do pretty well as a gnome gunslinger.

[Melkiador]

Once you have 6 players, the action economy gets really wonky. Your party will tend to burn down most significant threats in a round or two. A gunslinger certainly does well in that environment.

[My Self]

Most martial characters are forces. Most casters are force multipliers or enemy force divisors. Some casters are both forces and force multipliers, such as archer bards and battle clerics.

So what you've got:

Aasimar Cleric (Force multiplier and force)
Hunter (Force x2 and force divisor)
Paladin (Force)
Fighter (Force)

Combat-wise, your party is heavy on force and light on force division. If you want to become hyper-effective, you could toss in a primary force divisor (Wizard, Psychic, Sorcerer, Mesmerist, etc.) and a force multiplier (Bard, Skald, Wizard).

Additionally, unless your Paladin has a good INT, your party will be lacking for social skills. Hunters get a lot of skill points, but aren't known for high CHA.

[Driver 325 yards]

Here is some advice on a Bard Archer God

[Ascalaphus]

A gnomish buffing/controlling bard could be a good fit in that party. The hunter, cat, paladin and kobold will all benefit from Inspire Courage (write some cat songs!). Your cleric could use a colleague when it comes to battlefield control. And you bring a lot more skillmonkeying to the table as well.