OK, I thought I had this in the rules, but it isn't there. So in the event of a Lance Leader retirement, you can either create a new PC using the standard Lance Leader Creation rules, OR you can promote your XO to the Lance Leader slot. However, the rules for the latter aren't in the document. So here they are:
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Alternatively, you may choose to promote your
Lance XO (and only your XO) ANY MEMBER OF YOUR LANCE into the Lance Leader slot. For the remainder of the contract, the new Lance Leader must operate on whatever skills they have available to them without modification. Following the current contract, the new Lance Leader will receive a small number of points to flesh out their skills into a full character, representing their extremely intensive "on the job" training and blossoming into their current role. The new Lance Leader - upon completion of the contract - will receive 6+1d3 points which may be directly added to any or all of the following Skills: Administration, Bureaucracy, Leadership, Negotiation, Scrounge, Strategy, Tactics
Using these points, no skill may be improved by more than 2 points, no skill may be improved to greater than a +3 rating, and no more than one total skill may be improved to a +3 rating. Thusly, A character who started with a +1 Tactics may spend 2 points to improve Tactics to +3, but may not also improve their +2 Scrounge skill to a +3. A character who started without a Strategy score at all may spend 2 points to improve their Strategy score to a +2 rating, but no higher. If points cannot be spent because the above limitations make the expenditure impossible, excess points are lost.
EDIT: Yes you still get the SPA XP and other stuff from the rules packet.
EDIT2: Promotion into a Lance Leader also requires Attribute Generation. Each non-edge Attribute is set to 3+1d6, where a 6 = 0. This produces a range from 4 to 8, which guarantees that Lance Leaders will not be disqualified from MechWarrior status due to low rolls, and the Trait System caps at 8. For Clan Trueborn MechWarriors only, when rolling for your DEX and RFL Attributes, a 6 actually counts as a 6, producing a range from 4 to 9. Finally, add +1 to your EDGE score, to a maximum of 3.
You also gain 3 Trait points which may only be spent on Traits (not SPAs). You may also take up to 3 negative Traits to give yourself additional positive Trait points (ie, take Stigma/X to offset a Contact/1).
The intent of this is to make promotion viable as compared to a full generated MW3 character. This is been hugely out of balance for an extremely long time, and I'm sorry it took this long to get it right.
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Since it appears that the clan tech knowledge skill is becoming more common, would it be possible to add as an SPA purchase limited only to techs?
No.