Im all for makeing the Malakin a Trader-Civ and strong ally in one way or another.
If Kael doesn't want to go for the super-city approach with them though adding food per Trade route whould be a bad Idea. (sadly. I whould really like a 1/1/1 flat bonus but thats against what Kael outlined for them having no huge cities which it whould definately lead to.)
But what about 0/1/2 per Trade route with cities that have their state religion (or cities of civs running their state-religion) for them and 0/1/1 for other cities / civs trading (+sharing their religion?) with them? (As seen in Final Frontier, trade-route bonuses really work out very well gameplaywise.

And the AI should be able to grasp them fine as well.)
Making the bonus more complicated might make the whole thing more hard to grasp but might natrually be very interesting as well.
And i honestly see no real reason (neither in nor out of game

) why a bonus shouldn't extend to their own cities (no stack of 0/2/3 for own cities naturally.

). Thats what a nomadic trader society is all about. (in regards to the trader-part at least.

)
Unless of course the bonus isn't flat and special perks (free specialists and the likes) are concerned.
Foreign Trade Routes allready give a whopping +150% bonus for extended peace (which is another disincentive to go to war with an religious "ally") and another possible +100% for overseas. So trade with others is more beneficial anyways. Thats enough to not keep your borders closed. Also foreign trade-routes are prioritised because of it anyways by the game. (if im not mistaken the routes are assigned in a way they give the most yields for your civ. At least they definately change, don't know the exact mechanics of the changes though.)
Plus the benefits of a council usually (which in case of the overcouncil the Malakim are more likely to dominate than many other civs anyways.

). Also Overcouncil offers more with regards to trade-routes if im not mistaken so the synergy whould be allright there.
And with Varn (AI) in the lead there is no need to fear that he goes hugging with everyone.

Decius is another matter but his traits are less on economy anyways (and quite strong in their own right) so it whould help him compensate a bit and try a more "friendly" + "loyal" approach.
As for the XP-thing: Not an all to bad idea. And whould add up nicely to other things.
But! it whould make high-level Malakim-AI very! scary.
On Immortal / Deity Varn already goes explode + berserk in quite some games (presumably thanks to the way he conducts diplomacy with "a big stick" rather often while still beeing a tech trader and staunch ally to some in the game.) (On Deity i had games were he did beat Svarts (turn 60!

or so) to FoL (and rather often does dwarves to RoK) and in one game he founded 6! religions.)
Together with Command-posts from organized (either from adaptive or decius) its allready 6 XP (+ commando for Decius after the most recent Change). Add to that the Free XP on higher difficulties and he can pack quite a punch. (not that this is automatically a bad thing. It just may turn out as: too much. But thats something to be seen / tested by us anyways after you implement.

)
Whould it also effect the units from the worldspell then? (flavorwise presumably ought to. But don't know if it whould be to powerful. But that answer might have to wait until a change is allready planned...
On another note regarding Varns traits: Has anyone from the team considered to trade his fixed creative trait for financial or spiritual? I don't know why he is creative + adaptive (financial)?
Lorewise spiritual + adaptive (financial) might make much more sense, whouldn't it? (financial + adaptive [spiritual] might be another choice but sounds less fitting if perhaps stronger?)
I for the life of me can't understand why he is creative (neither by the patron, nor the leader, nor the civ. Only balance might have been the reson but i hardly see a danger there).
And it whould give another serious boost to their deciple-units. (except for decius. But he has decent Traits [imo] in his own right as mentioned allready.)
Also Spiritiual is not an all-to-common trait so there seems to be no big danger of overlap (unless i disremember...).
Also: Is it intended that the first pick for adaptive now comes later into the game (~ Turn 95, not around Turn 5 like it did some versions before) or did that slip through in one of the more recent versions? The frequency of a hundred truns looks allright in my book but beeing forced to one trait is not allways a nice thing (this is by far a bigger concern for the other adaptive leaders though. Since financial is a rather decent trait in its own right.)