If it doesn't get rid of something you really want or need, maybe look into the racial feature that gives the Teifling large size arms, so whatever weapon you are using for melee would be size large without penalties.
Craft your own alchemical weapons with swift alchemy and the grenadier archetype. Lose Brew potion (so less party support) but you can take infusions to hand out buffs, of which you will have plenty thanks to decent INT.
Then you can apply alchemical weapons at 1/3 cost plus INT to damage on your first successful strike. So your 1st weapon will be mutagen STR boosted, weapon damage, STR damage, Alchemical weapon Damage (Negligible at higher levels but not nothing and with some ok rider effects), INT if the weapon was one that would have splashed, plus enchantment son the weapon itself.
This looks like a decent melee build, the low CON will hurt you, and you cannot throw bombs in melee without taking AOO's. Going the TWF route will let you throw 3 bombs a round, but lacking quickdraw you cannot get 2 blades in your hand and attack in one round if you are suddenly threatened either. Tieflings can trade Darkness spell for claws or a Bite attack, which might be nice depending on party and whether they have Darkvision or not, its a handy spell to have depending on party and game so not sure if it is worth it, but it would save a discovery you could use for other things. like fast healing 1.
Prehensile tail is Amazing for a grenadier, swift action to ready alchemical items for application, or to ready a second melee weapon without Quickdraw (free action switch "hands" on your turn).
There is also a trait that grants extended duration on Mutagens.
I would drop INT to 16 or STR to 10 and raise CON to 14,
This, or else get spontaneous healing early. Even if you do get that a melee guy is probably using buffs rather than save-based effects and will want str or dex more than int.