I agree, the impression from the books is that the missions were short term jobs. Absolutely. Unfortunately, I just can't see anyone actually running a war this way and I think a significant portions of combatants in this war would be mercenaries.
There are so many players in the "war" that many of them do not need long term mercs.
You may have a mission to harass a local plantation, slowing production, so that your employer can get a supply contract since the competition is unable to ensure delivery.
Don't forget the job you get so the employer can deny responsibility.
You may even get a job supporting another mercenary company.
But for all the other missions, for the most part I think they would either have multiple parts to them indicating a larger number of total days hired (not necessarily back to back), or (more likely) the exact time to completion may not be known.
For garrison duties... I just don't see a three-day garrison deployment.
Some missions do not fit the short or fixed time models.
Garrison duty (by the formula) pays for a short fire fight every couple weeks and a lot of down time.
Recon needs a little adjustment. The base is what the employer thinks it should take, or what they are willing to pay for. Try adding in additional points to the contract such as a bonus or release for early completion. Maybe the players already know what the employer wants and just makes a quick check, work three days and paid for twelve, already negotiating for another job before the first was expected to be over. Another point may be extended missions, do you get paid if it takes longer, at what rate, how does it affect future contracts with them.
Most employers will not want to pay for your down time, might as well create their own team if that was expected.
I'm also assuming that most of your missions involve secondary objectives. That's something the book doesn't really cover very well.
Good catch. I would handle these as bonus pay rather than contract points.
As contract points you would have to add mission base cost and TTC. A twelve day Recon mission might include two assault and one interception. Players insist they be paid for twelve day recon and a day each for secondary points even though the times overlap. Employer insists that pay be all or nothing.
As Bonus the mission is paid for the time of the primary assignment, twelve days recon. If they complete the secondary missions they receive partial base pay. One assault may pay half base, the other three quarters, interception one quarter. The team has the option to ignore them if it would interfere with the primary mission. If the recon takes them away from the initial area the may not be able to make the interception.
You can still research the job, the client, and any potential competition just as normal. You're just paid more, and time is kept track of in abstract approximations. This aids both in helping the game/world make more sense and aids with my own bookkeeping.
Different play styles, some groups like to track time. I'm in a campaign where we missed a festival by two days because the wizard insisted on making a magic item.
Just from the way I setup my campaigns, I prefer to think that a lot goes on between missions and between sessions and that the parts we play out are just the dramatic highlights. It seems weird to me if you become a famous mercenary veteran in only a couple months of game time. If each mission lasts for several months, with one or more months in between each mission, the game's calander makes a lot more sense to me with a campaign spanning years of game time.
IMHO the experience awards suggested in the book make for excessively fast advancement. Advancing a level on your first mission seems a bit much.
Taking an idea from 2nd Ed AD&D I would grant experience based on mission enhancing actions.
100 Successfully research employer and job
100 Negotiate contract
10 each additional point in teams favor
20 Failed negotiation/ lost job and review why
100 Complete primary mission
20 each secondary objective
50 Reduce combat efficiency of enemy mech (weapon, limb, sensor inoperative)
50 Immobilize enemy mech.
200 Force enemy from combat area greater than one week (resupply or repair)
It's ironic that you use the example of the auto mechanic. Would you pay them a retainer fee so that he's on hand when you need him or pick a mechanic only after you have a problem? Well I get your point, according to the rules this is exactly what you do! You buy a general service contract so that you'll have the mechanics handy when something breaks down. It's the next best thing to having your very own repair shops. Mercenaries could be thought of under a similiar light.
The difference is that the repair shop is able to do other jobs as well.
For long term contracts, like six months, where the team is obligated for any mission the employer assigns I would handle things different. Start with a retainer fee of $100,000 per month.
Additional contract points as usual, extra pay, support etc.
i.e.. The team is willing to use their own computer and intell sources (spy satellite subscription) for all missions. In return the employer (who lack such resources) will provide air support once per month and infantry support five days per month. The team is willing to loan their Intel support staff when not needed for missions for an extra 20% monthly fee.
Such long term contracts may have other terms. The team may be required to provide non combat services during down time, such as training junior mech pilots, assisting with repairs. In effect the team and all their staff become temporary employees.