Been reading this thread for a few days now and it's sort of sparked me off.....
It's quite late here now so it won't be a long one..... *everyone sighs*
There's a couple off thoughts that occurred to me to add a certain amount of uniqueness to them.
1) Jungles are always renowned (infamous) for their poisons, so poison use would be almost a certainty, how about a hidden resource (same as lanun pearls) that when obtained allows poison blade units to cast a spell similar to "hold" freezing the target in place for x number of turns or maybe slowing them down... they are after all slavers and it would be very useful in that line of work. Also not bows...blowpipes!
2) I don't know if this one's possible but due to their synergy with with jungle, all units (or maybe just recon) have increased visibilty when within jungle... its a major boon as the great danger in jungle (I find) is simply finishing your move adjacent to a barb/animal, without being able to see it comming. Possibly also jungle invisibilty for recon.
3) extra bonuses or unit/building ties with existing jungle resources, sugar, dyes and banana...... OH NO ..... +1 BANANA AFFINITY!!!
4) I'd also suggest very little in mage line... adept only. But really push the herbalist/ druidical /nature priest side.
Do people envisage a high tech ability ie libraries etc? Or maybe slave for research without going AV path