We should just adopt all the civilians that want to use force walls
How do civilian / ninja joint ventures work? Rather than selling a Force Wall seal (thus requiring you to go through the Tower's right of first refusal), can you rent a device that includes a Force Wall seal to a carpenter or mason?
If not, could the carpenter's guild hire you for a mission and pay out a combination of cash now + a bonus calculated as a percentage of (revenue generated or costs reduced) by the ninja's efforts?
So, why not play with that value? Hazou has the Iron Nerve, which guarantees perfect blanks. For your average sealmaster, a bad blank will often mean serious risk of injury or death, and they should follow a Poisson distribution, meaning that the probability of producing one needs to be very low for this not to constantly kill sealmasters (or maybe that's what actually happens? It's another possible angle). In other words, just decree that normal sealmasters obsessively check their blanks, using up a lot more time - say 30 minutes per blank total, and not more than 10 blanks per day because of the required concentration. I don't know if this is enough to solve the problem, but it should help.
This would increase seal scarcity by a factor of 3-12x depending on the number of elements in a given seal, raising price per seal drastically. As you mentioned, Kagome would need a mechanical effect that allowed him to produce seals faster in order to justify the Goketsu keeping hundreds of explosive tags in bowls.
If Kagome is able to make a blank every 10 minutes, and Hazou every 5, while other sealmasters require 30, Hazou alone would comprise a full
20% of Leaf's seal production. But Kagome's previous feats of seal production and profligracy (he casually uses ~10+ seals every time the party sets up camp and dozens - hundreds when fighting seriously) imply that he can produce seals even faster than this.
Moreover, this would give Hidden Mist an enormous economic and armament advantage if the Kurosawa ever mobilized for seal production (bounded by the need for training and the % of Kurosawa with general aptitude sufficient to practice sealing). But if the Kurosawa bloodline granted such an enormous relative advantage for sealmaking, would they really not have dedicated themselves to the art? It's one thing to turn up one's nose at a practice that could increase clan revenues by 20%, quite another if it were 120%.
Shikamaru also used Seals extensively during the Chunin Exams.
Consider the demand for Seals:
Life-Saving Purifier: Every ninja without defense against poison gas would ideally want a few on hand.
Air / Earth Dome, 5SB: Defense scaling with the skill of the
Sealmaster, not the ultimate user. Can be used by Clans to equip their heirs with emergency defense against chunin / jounin level threats. Useful for virtually any ninja that wants defense without spending chakra.
Explosive Tag, Goo Bomb, Banshee: Offense scaling with the skill of the Sealmaster and the number of seals present, ranged / elemental / aoe offense without spending chakra.
Skywalker: Goes without saying
Storage Seal: Logistical range extender, versatility extender
Banshee Slayer: Necessary to defend against Banshee for all those without specialized or highly broad defensive techniques
Bioseals: Whatever the fuck Arikada could do
Say in an ideal world every Chunin and above (~270 ninja) would receive a reserve of 8 Skywalkers with that reserve being replenished every time they return to the village. If they take 100 missions per year and use a parsimonious average of 2 Skywalkers per mission, demand for Skywalkers alone (54,000 / year) would eclipse the entire jounin-level seal production of Hidden Leaf (36,000 / year). And that's assuming 3 full jounin Sealmasters (10% of 30 sealmasters), whereas in reality jounin only constitute between 2 and 4% (30-50 of 1500) of the ninja population.
If you hold ~20% of seals in strategic reserve for wars, every Chunin+ ninja of leaf would only be able to use an average of 1.1 jounin-grade seals per mission.
In reality, it's more likely that the jounins horde most of the jounin-grade seals, since you may need 5-10+ to make a difference on an A-rank mission. Making friends with your generation's sealmasters or having one in your clan can be a matter of life and death.
There are also clans like the Hyuuga where Sealing expertise is necessary for the perpetuance of their traditions (the Caged Bird Seal). They need to make sure they stay on the cutting edge of Bioseal Tech because if anyone ever 'hacks' the recognition code for Caged Bird,
their entire clan can die to a single handsign. Convenient how every Kage with legendary levels of Sealing (Jiraiya 80+, Minato 90+) has died before their time...
There's a lot of exceptionally fertile farmland inside the wall that is able to support a noticeable fraction of the city's population. It's probably ~5:1 for farmer:koku production, probably because unique chakra bullshit in the soil the presence of which was a big part of why Hashirama chose this spot to found the village.
Hm... historically 1 hectare of land (worked by 4-5 farmers) produces 10 koku of rice per annum (2.2 koku per farmer, a surplus of 1.2 koku per farmer as 1 koku feeds 1 man for a year). If it took 5 farmers to produce 1 koku per year, that would be significantly below subsistence level. Do you mean that Hidden Leaf produces 5 koku per farmer, a surplus of 4 koku per farmer per year?
That would free up 80% of the population of Hidden Leaf for non-agricultural tasks and/or raise the GDP per capita of Hidden Leaf by 227%, a localized GDP per capita of (572 in 1990 dollars*2.27*1.955 conversion to 2019 dollars) = $2,538 in 2019 dollars. Should be fine, it's only a 12% increase to Fire Country's output as a whole, though if a large percentage of Fire Country's cultivated fields are that way (right now only 115,000 of the country's 15,600,000 hectares are under cultivation, .7%, so people have freedom to defend the most fertile areas) then the GDP per capita of Fire will be about twice as high as in my Prices post.