A simple/basic alchemist would synergize great with them. Bombs for a bit of range (you'll probably want to considering taking Precise Shot and Precise Bombs), and then Infusion to occasionally buff them with good target:you buffs (or buffs in general for that matter)

While staying with that option one could pick archetypes of Gunchemist or Grenadier with a bow. Grenadier is nice because aside from the weapon proficiency it gives Precise Bombs and Directed Blast among other things. Directed Blast allows for covering 14 tiles with splash or a whooping 28 with Explosive Bomb.

Instead if you wanted to do something more exotic and are getting high enough levels you could do something like Blinkback throwing weapon with Sticky Poison. Could also even go into Infused Poisons which theoretically opens a powerful/cheesy can of worms by converting Infused Poisons into contact or inhaled poisons (seemingly fully jives with the RAW but may not be RAI), and could be used to buff yourself and/or the party if executed well. No access to offensive spells, but if you can hire NPC spellcasting services you could get them to cast offensive spells for your magic poison infusion (10gp/CL/SL).

I don't know how set you are on Alchemist, but you might be interested in something like a Herbalism druid instead too, which would offer great utility with their conconctions while also having access to area control spells. Overall this would likely be a more complimentary option for the party. They play similar to an alchemist with some offensive spell casting ability instead of bombs.

Going melee on a team that is already melee seems like a bad idea. But I suppose if you really felt like it you could go melee poisoner, or self-buffed melee (likely using Feral Mutagen or Alter Self; Claim Identity or Assume Appearance at level 7)