Following the other thread, here is my "skill system", which works on top of existing BECMI mechanics. It's still a draft, I have started testing it, so something might change in the future, but the "core ideas" are here.
Talents
by Antonio EleuteriTalents can be acquired in place of weapon mastery slots (or slotted differently at the DM discretion). At first level no more than one talent may be selected.
Horsemanship
The character can attack also while his war horse is attacking. The character can identify the quality of horses (number of hit dice and hit points). The morale of the mount increases by +2.
Healer
The character can restore 1d6 points when treating wounds after a battle (Judge's Guild Shock Rules). The character can also provide a +1 bonus to Saves vs. Poison, in case the poison is not immediately deadly. If the optional rule for poison effects is used, the damage is reduced by 1 per monster hit dice.
Leadership
The character improves the Loyalty score of retainers by +2. He also adds +2 to the leadership Battle Rating score. The number of retainers doubles (before applying the Charisma modifier).
Outdoorsman
The character increases the chances of foraging (1-4 on d6) and hunting/tracking (1-3 on d4). The character also reduces by 1 the chance of getting lost. The chance of evasion during wilderness encounters increases by 10%.
Seamanship
The chance of a storm crashing the vessel are reduced (DM choice). Boarding actions receive a +1 bonus. The character is an expert swimmer and he need not check for swim even with armor.
Tactics
The character receives a +1 bonus to Initiative checks (for groups). In War Machine rules, he can shift one position on the Tactics table after seeing the outcome.
Alertness
The character reduces the chance of being surprised by 1.
Brawler
The character increases his Wrestling Rating by +2. He inflicts a –2 penalty to unarmed combat saves.
Linguist
The character can choose another language. Depending on his intelligence score, he will also be able to read and write in the new language.
Oratory
The character has +2 to Reaction checks.
Perception
The chances for detection and to spot secret doors increase by 1.
Stealth
The character increases the chance of surprising opponents by 1.