I think that there should be more than an indirect cost and benefit to having an adventurer friendly nation though. If you provide a hospitable place for adventurers to resupply, adventure, and eventually settle down, assuming they survive (bringing all that sweet, sweet loot with them), there should be some pretty direct consequences from that.
First off, adventurers would come to your lands more than the neighboring lord (who happens to kill adventurers for the fun of it). They should buy from your shops (bringing you a bit of tax revenue, and providing them with better equipment), stay at your pubs (where you should be able to offer jobs to them, or have them take jobs from others), and eventually ask for a nice little plot of land within your territory to settle down (where they can build a residence, which would depend on the type of adventurer they are for what type of residence they build and what can happen there).
But what is more, within your territory they should be seeking out places to adventure, and getting rid of problems for you (if they like you). However, if they are a more nefarious type of adventurer, they should be seeking to cause you problems. Example, one enterprising young "adventurer" might decide that raiding your caravans is a useful hobby, prompting you to have to assign heavier guards to the caravan or hire more friendly characters to hunt him down.
That leads me to point number three. Right now the character recruitment system is pretty inflexible and impersonal. While I think this will get better as the betas go on, I would like to see two ways of interacting with characters, only one of which is semi-modelled now. First, you can hire them directly (as we do now), they will charge a salary (based on their level), and you get complete control over them. These will be your "enforcers," state adventurers, state merchants, thinkers, administrators, ect. They will be costly, and will get more expensive as time goes on and they get better at what they do. Then, there are your friendly adventurers. These guys you can hire by job or by time period (guard this caravan or city for X amount of time). You do not get direct control over them. You pay them a one time fee, or a small fee up front and a bigger fee at the successful conclusion of their task. The percentage of the loot they get to keep is the subject of negotiation. After their task is complete they go on their way. An advantage of being an adventurer friendly nation is that there are a lot of NPC's who flock to your cities that you can now "subcontract" jobs out to. The downside is that those same NPC's could be out there stirring up problems and, occasionally, taking direct action against you.