When it comes to the architecturally superb “Func Map Jam 9 - Contract Revoked”, I played it on a “Normal” difficulty level and from this standpoint, I call some combative setups simply unfair. On the other hand, we all are aware that within the terms of an episode or a campaign, there is certain difficulty level escalation, as well as the protagonist power escalation; things round up to a final fight, which should be difficult. In a jam, every map, can be a final fight map; there is nobody telling otherwise.
Jams, by nature, tend to be quite random, to a degree for sure. With the “Func Map Jam 9 - Contract Revoked”, the artistic spectrum, was very coherent, albeit the jam nature of event, showed in the realm mentioned - the difficulty level, was all over the place, such as you said.
Some of the blame, could perhaps be put on the lack of experience and overt fascination with the ‘Quoth’ novelties; thus underestimating the further impact the mod would make on the difficulty scale - but you decide, whether this argument, is that much convincing, since we speak of a second ‘Quoth’ iteration already.
For the difficulty level measure, I think it should be something of mathematical nature; certain sums of relevant parts, need to balance out. Understandably, this is not a bulletproof solution - there are also environmental factors and other elements of more qualitative than quantitative nature; albeit, maybe even these, could be given an estimation value. Anyhow, I do not really know how to bite the problem, where to begin, what to suggest. It takes experienced mappers for that kind of job and I do not really believe plenty of people would want this; to restrict themselves. Other question is - is it worth of the human energy investment to carry out?
For the general project outline, we would need to gather all relevant parts influencing the combat or otherwise valid in combat, assume that a map divides into sections and the balance, needs to be measured for each section independently. The map section, I see as a space where the protagonist, may roam openly - even if “openly”, means just back and forth - to possibly replenish the resources, even in the midst of a combat going on. Therefore, if a combat setup shuts off all escape routes, it is counted as a section. Some larger sections, could understandably be broken down into sub-sections, for strategic resources allocation.
Speculatively speaking, there is no other way but to simply start with a draft - even if it was silly - in order to see what does it tell, if it does make any common sense against the experience and perhaps then ask a question, what direction the alterations need to go next.