A few beliefs (to be tested this weekend) from my perusal of the export_descr_guilds.txt file to add to the OP.

The structure of each entry in the file looks similar to below:
;------------------------------------------
Trigger 0004_Normalise ##TriggerName
WhenToTest SettlementTurnStart ##When triggered

Condition I_TurnNumber > 25 ##Condition to be met

Guild all s -1 ##(Category label) (guild type(or all/this keyword) (a,s,o) (#points)
So what i think happens is that the game keeps a running tally of how many points each settlement has 'earned' towards each and every guild type.
When you meet a condition points are assigned either to a=all settlements, s=settlement that triggered, o=all other settlements. I believe that's what the letters stand for as all triggers with 'a' points are for things like trade agreements and the actions of spies, assasins where it doesn't make sense to tie things to a particular settlement. As well, some triggers give both 's' + 'o' points, or, 'a' points, but you never see 'a'+'s' / 'a'+'o'.

As well, I believe the OP is wrong on the normalise value - you lose 1 point from every guild tally in every settlement every turn after turn #25, not every 25 turns.

Ok, so that's great info for the modders, but what does it mean for play, huh?

Well, explains why i always seem to get theives guild offers so soon - every spy mission adds to tally for every settlement, throw in a couple of brothel-line buildings, and spy trainings at a particular settlement and voila = theif guild offer. The assassin's/Hashashim guild works much the same, just a little slower as there's less/harder triggers.

So, use those spies, assassins, priests and merchants actively ie don't just let them sit there doing there passive thing, make them spy, kill (not sabotage??), burn and acquire.

Some guild-specific tips:
Explorer's guild - train merchants and send fleets to far away lands

Alchemists/Swordsmith's guild - train and build gunpowder/sword line stuff (units as listed in OP).

Might be obvious, but appears Woodsmens guild is England faction only based on this file alone let alone any hard-codedness that might exist (would be very difficult for any other faction to get, esp anything higher than 1st level).

Mason's guild - will take a while just build, build, build as per OP

Horse breeder's guild - a tricky one as is city-based guild but really requires the training of cavalry to level up (except I think muslim factions can easily train cavalry in cities). Tip: as spain produce Jinetes from the plaza del toro. Not sure about workarounds for other western factions (races maybe), if none exist then u'll just have to produce 100's of cavalry from your castles!!!!

Various Knight's Chapter Houses - Hospitaller's are easier to get than Templars. Hospitaller's (St Johns) have extra triggers to earn points - DoW on islamic factions (no need to actually fight battles!!!) and neighbour islamic factions.

Can't see any workaround atm for muslim factions re swordsmith guild catch-22 (have an idea but need to test it....)

Also, need to test - if reach points for two guilds at same time, what order are guilds allocated in? Do you get a guild offer the moment you satisfy the threshold, or does this just satisfy part i) of a further random chance condition?