I agree, both would work well as counters. Especially Chandelure (who makes a fantastic revenge killer in general). My set for him includes Psychic, which should be able to net an OHKO. As for Gliscor, there is very little that Emboar has that poses a threat to him (barring Scald), so he'd get a very easy switch in.
That's why I recommend against just slapping a Choice Item on Emboar, as it does not really function well with one.
Chandlure Burning Emboar...lol.
Gliscor DOES fear Scald, although a STAB Fire Blast or even Flare Blitz WILL do a lot of damage (Gliscor does not resist Fire).
Pre-Evolution Corner
Anyway, Pignite, point for point, outdefends Emboar when Pignite has an Eviolite. On the other hand, Pignite does not have access to Scald or even Bulk Up (it gets Curse and Work Up though). Pignite exchanges Reckless for the polar opposite Ability Thick Fat, although with Pignite's natural resistances this is rather moot. Still, if you would like to use defensive Pignite, play at your own peril. Should Emboar find itself banned from the lower tiers, Pignite can also find itself utilizing the Flame Charge or Choice sets, albeit with significantly less power due to no Reckless.
Tepig does not have a niche to find itself in for LC. If you wish to utilize Tepig, Curse, Flame Charge, and Choice sets are all still perfectly viable. After all, Tepig does still have access to Flare Blitz, Head Smash, Wild Charge, and Superpower.