Thank you all for your replies and insights. Once again, i am impressed by this community.
Here is what i am working on now and an example (warning, i am an old timer and i use the word die rather than dice to refer to D#, but you can blame D&D for that):
Current focus: new economy system with light, dice based book keeping. Uses fixed dice to track gold spent on tasks and resource depletion. I have 2 systems in mind, a simple system and a more advanced system for the more detail oriented players.
The advanced system uses Task Cards that have a D20 attached to them (so far i came up with 4 types of Task cards: Travel resources, Training, Recruitment, Research) . Each task Card, such as travel resources, which represent rations and travel equipment or animals, starts at a very low number. But the mercs can invest by purchasing travel resources, and thus increasing the die value by 1, i.e. increase the D20 to a higher value, so from a 3 to a 4 etc. The cost to increase the resource die is not fixed as it can be modified for several turns by events, such as war, peace offerings and rebellions.
This creates an incentive for the mercs to always stock up whenever they can afford so to evade being stuck in an area when something really bad happens. I am preparing events that can affect the world, and that can be randomly determined in PEF like manner.
In addition, Items have a fixed die assigned to them. Every encounter a d6 check is made and on a 1-2 the item's fixed die is lowered by 1, so a 6 becomes a 5. . To simplify, i use D6s only, but D8, D10 or higher can be used. When the item die reaches 1 it must be replenished or repaired, depending on what it is. A shield will need to be repaired and an arrow quiver replenished for example. If the item is not replenished or repaired, it will run out or break and a new item must be bought.
Example: a contract.
It can have 6 random parts:
Who: employer's name, title and location
What: Basic description of the task
Where: the destination for the mercenaries- the location or collection of locations/route followed.
Opposition: enemies, antagonists or events.
Reward/Penalty of failure.
I think the PEF system is perfect for creating the opposition. The location can be determined randomly and it can depend on the method players use to track their travels. For example, a hex-crawl type can use # hexes away from the employer's location. That can help determine the Challenge Rating of the Contract and the overall reward. The number of PEFs/evens would then factor in the reward. So if a player had to fight 10 PEFs to make it to the destination, the amount of money offered would increase to reflect the work that had to be done. Mercs have to eat after all and they would have never encountered that resistance if it wasn't for the contract.
Player meets a Noble who was "kicked out" of his land by nasty rebels- or so he claims. He seeks revenge. The player's Company can do that for him- for a hefty price. Then the Player rolls on location table i.e. 2D6 to determine the destination in terms of distance. The player then rolls the Opposition table to generate a set of PEFs that will "reside" in that area. Based on what the Opposition is, i.e. a rebel army, the player will roll for involuntary encounters as normal, for every day of his/her trip, but the encounters will be generated from a new table rather than the "stock" WHL table. The new table will also include members of that rebel army that are attempting to stop the player from ever reaching the area. Of course, generated PEFS in the final destination, can randomly act: maybe the rebels expanded their operations, and now control more "hexes" or "areas". This will create a sense of urgency for the player to finish the contract before it becomes too difficult.
Also, to make things "tough" for the Mercs, each contract can have a "surprise" element to it: maybe the noble lied about the nasty rebels and they were actually a larger army or a wizard was involved. So, upon arrival to the destination, the player would roll against a unique table that would define what and if a secret element was "left out". If yes, the table would present a "twist" and specify how that affects the contract. Maybe more $ for their trouble or possible recruits, assuming o course the Mercs make it though and return to the noble.
More to follow soon. Once i have tables ready, i can upload here for people to test, and we will have a balanced AND fun system soon.