In Eberron during "The Last War" House Deneith, like all dragonmarked houses remained neutral and sold their services to the highest bidders. But as mercenaries/soldiers this could lead to some unique problems.
While these 2 situations appear different, their core problem is the same. Were either of these (or similar) situations addressed in any official material?
What would happen if 2 opposing countries had hired House Deneith soldiers in their units on the same battlefield? Would they fight themselves or did they have some contractual limitations to their services that excluded such a possibility?
While I'm sure House Deneith mercs were expensive, at times it could potentially be more cost efficient to lose them than a country's own citizens/soldiers they'd spent time/$ training and which would still be needed later in the war. Therefore, if presented a situation where heavy losses would be expected (think D-Day or worse) could they/were they ever ordered to (near) certain death? Was there some sort of financial penalty for mass losses? (This is the only penalty I can think of to prevent such tactics)