I like this version better, Frank.
I'm always a proponent of the concept of "less is more". The information herein is sufficient for both player and DM, and it seems there is certainly a nod to old-school "rulings not rules" mentality in the writeup. It's verbose, but that aligns well with BECM.
Things I like
I like the inclusion of Amateur, but I would remove it from the skills listing on page 1 and keep it only on page 5.
I like the inclusion of Multiple Actors and the examples given. It is a good baseline for DMs to use for assistance.
I like the specification of both Partial and Penalty. Sometimes applying a penalty makes something impossible that shouldn't be, and partial covers this nicely.
I really like the mention of $$$ as the most common modifier for Guild and Networking. Good for DMs and Players, and a great way to manage the GP bloat of mid and late-game BECM.
Things I dislike
I have always disliked the modifier you've mentioned in trap search, wherein the DM is asked to modify the roll by -x in relation to the HD of the trap's designer. That seems like a mental exercise for the DM that is completely unnecessary, and wouldn't virtually ALL traps have at least a -1 modifier? It's not a bad thought, but as a DM I really don't want to sit down and think "what sort of person/monster made this trap? what was their HD?" Maybe all the traps in a ruined castle were made by a master trap-maker who is; like an Armorer, Animal Trainer, Sage, or Spy; more of a Specialist and thus doesn't have or use HD. Tucker's Kobolds wouldn't work under this scenario without adjustment by the DM; which you graciously suggest in the Preface, and most DMs know anyway, but that's beside the point.
I would much rather see you offer DMs a better descriptor on how to apply penalties based on a set of circumstance. Example for Trap Search:
Modifiers: When designing a trap, the DM should annotate any modifiers (generally penalties) which might be applied due to extraordinary concealment of the trap, auditory or environment distractions or difficulties, design of the mechanisms, magical enhancements, and so forth. These should not be applied to all traps, but on occasion to traps for which there might be special circumstance or those guarding a particularly wonderful treasure.
This forces a changing dynamic of thought. The DM isn't asked to think about the designer's HD, but rather, the purpose of the trap and the environment and circumstance in which it lies.
The Time paragraph under the Modifiers paragraph. It suggests double, half, etc. But it does not give a baseline and that's something that should be given, otherwise, a DM might waffle on time under the pressure of the players. The player could argue that it only takes 20 seconds to pick a lock, and players will certainly pressure a DM for every advantage (as they should). A strong DM would simply not cave, but many DMs are a softies underneath, and having a baseline would, IMO, be better. I would suggest 1 round for Listen, Climb, and Stealth (Climb may be performed in battle, the others cannot) and 1 turn for Search and Fingerwork. You do give time for Appraisal, so it would be fitting to include such in the description.
It is unclear in the Appraisal description on how to apply variance. I assume you mean the ± is meant to be read as a percentage of the overall value; i.e. Furnishings would be ±10% of the actual value. If I am wrong, please correct me. Also, I would personally change the Appraisal from 1 round to 1 turn, except in small quantities (i.e. it's easier for a party to count a 500gp pile of coins then to have a Jack appraise the pile). Regardless, this is a minor quibble at best.
I would like to see Buy (under Networking) changed to Find. Resources aren't necessarily things you buy (though, you may have to pay to find that resource). It could be people of a specific nature (sage, spy, trapmaker, etc.) or even people who wish to remain hidden (someone in a safe house, for example). It, of course, can refer to items or objects, but I would like to see it expanded to explicitly include people and information. A successful check might give the Jack a means or knowledge on how to find the history of a person or how to find something that might provide leverage over a political adversary. Find just seems like a much more robust term.
Finally, in the final version, I would like to see a complete write-up that follows the same general flow of other classes in BECMI. Jack --> Description --> XP/Title/Spells --> Other Details --> PR/HD/Armor/Weapons etc. You can accomplish such without stepping on IP by changing layout and presentation. This would give it a full BECM feel and make it seem like a new class concept from the author. Of course, you would also add in Read Lang. and Read Scrolls in the description. Just my 0.02
Thanks for this, even in its current state, it's incredibly useful.
Oh, one more thing, I like it enough to replace thieves in my game completely with it (given my listed adjustments above). I would rather see you change it back to Thief from Jack, but that's another personal pref. The only thing you've removed is Pick Pockets, and that falls nicely under fingerwork. So, I would call a spade a spade, and just rename it back to Thief. It works (rather well).