Holy... How???
I used the dot system for Mechwarrior development. Split up the various 'Mech weapons into categories and the piloting and jumping into different weight classes. Put familiarity with individual 'Mechs as two-dot categories. I also had a list of personal combat skills (rifles, handguns, bows, etc.) and used many of the skills associated with WoD's Mage and Vampire (Alertness, Diplomacy, etc.).
Translating from the WoD system to Mech combat was simple. You start with base 4 as per normal, then you apply all bonus and penalties. Each dot in the category corresponds to a bonus of 1. If you are totally unfamiliar with the 'Mech, you had an automatic 2 point penalty to everything (hence the two-dot system for familiarity). So if you have 3 dots in SRMs and there are no other penalties or bonuses, but you are unfamiliar with the 'Mech, then you hit on a 3+ (4-3+2).
Out of Mech combat used the WoD combat and wounds system. For example, 3 dots in Dex + 4 dot in rifles = 7 d10 rolls (usually vs DC 6). Then the defender makes a defence roll, which usually equal to the armour rating of a given armour (e.g., he had a flak vest on with AR 2, then he made 2 d10 rolls vs DC 5). Damage = number of your success - enemy's successes on his armour rating roll.
Initiative is rolled via Dex + Perception + d10 every round.
Other non-combat skills are as per WoD's success system.
The system basically awards Mechwarriors who stick to a single chassis type as you will tend to have higher gunnery using all its weapons, a higher piloting and jumping skill in that weight class, and full familiarity with the 'Mech itself. Of course, since people tend to start with light 'Mechs, upgrading to a heavier chassis could be both a blessing and a curse.
I also have a fixed XP gains table and a flexible one. For example, killing a 'Mech gains you 1 XP on the fixed XP table. Since players can control more than 1 Mechwarrior at a time, it can become a strategic choice who to award the XP to. Flexible XP are given for RP reasons.
You could also buy Luck points at the cost of 5 XP per Luck point. Luck points allows you to force a reroll in certain conditions, usually those to avoid an event which can cause the instant death of the Mechwarrior. For example, if your Mechwarrior suffers a PPC hit to the head, you can force the enemy to reroll the location roll before I (as DM) start rolling to see if the shot hit a critical or not (which could be the cockpit, killing the Mechwarrior instantly). The shot still hits, but it just miraculously divert to somewhere else (although it is possible for me to roll another 12 and still take a shot at killing the Mechwarrior outright).
