Rub a dub dub,
Three fools in a tub,
And who do you think they be?
The butcher, the baker,
The candlestick maker.
Turn them out, knaves all three
The Spy: a full-shenanigans B/X class
Your butcher has always been a bit odd, and did not know the difference between sirloin and ribeye. The baker also, but for the opposite reason: he was honest and delivered always full-weight loaves. The candlestick maker gilting was great but the candlesticks were clearly not well lathed.
That’s because they were not tradesmen.
They were knaves.
They were competent spies under cover.
HP, Saves, hitrolls as clerics. Primary stat is Charisma.
Coverup: the Spy gets some basic training in whichever trade their title is. So level 1 spies get basic training as butchers. At level 2 as bakers. Level 3? Candlestick makers. The problem is that sometimes they are not that competent, but often it does not matter. So for expert tasks they get only a 3-in-6 chance of success modified by their reaction bonus: they might not do a great job, but they are great at selling themselves.
Three fools in a tub: spies in cities can locate another spy in 1d6 days and get useful something in exchange for something (material, contacts, information, safe haven, safe conduit are examples of what can be exchanged) if a successful reaction roll is made. Woe if the reaction roll fails.
Great Coverup: At level 8 they can either roll any of these rolls twice and pick the best result or have a 95% chance of coming up with a convincing reason, happenstance or coverup for the job not to be successful. For example having the workbench collapse, or the horse outside the shop to catch fire, or just mind tricks. Or, surely the best, they can convince you that you seriously do not need that gigot cop today, sausages will be better with turnips, or that, seriously Capitain, the mortar was somewhat cracked already.
Rogue Skills: use 1d6 Thieving, but starts with only 5 points. Gets 1 point per level gained. Or as a rogue of half their level, round up.
Agency: at level 9 Spies can set up an agency. They will attract 1d6 level 1 PCs per season, half of them spies, maximum one per Spy-master level. As they die, they will be replaced as long as the Spy-master does a good job of covering up their demise.