I have played with countless 2on2s randomers who got a flameHT. Even in high ranked, if you ask. They do work brilliantly, the idea is to use the undervalued mortar smoke to make good use of the FlameHT to destroy emplacements.
Keep in mind, that emplacements are expensive. If you really struggle against an emplacement player, well, just go elsewhere on the map, or move to harass their cut off points or their important resources.
If player go Bofors, that means no AEC, which is, right now, more advantageous for OST to invest into crew weapons and the 222.
If you really want to annoy Brits as OST, do a double pios opening, followed by double flames upgrades, mortars and MGS42. Always use smoke to cover up your tracks. Or use the artillery officier, who is brilliant too. Cover the whole mixture with Ostruppen, and either a quick P4, Puma, or FlameHT (depending what Brit is doing).