Some mods I found that add requirements on factions or guilds, before allowing you to join:
Oblivion
Adds skill requirements for the Fighters Guild, Mages Guild, and the Thieves Guild.
This mod centers on the Mages and Fighters guilds, changing them so that you will need to reach a certain proficiency in skills before being allowed to advance in rank. It bases on faction reputation + skill requirements.
This mod changes the Thieves' Guild quest "Independent Thievery", dramatically raising the amount you need to fence in order to get your next commission job, in comparison to vanilla Oblivion. There are two versions. The normal version (IThieveryRaise.esp) is tougher than Vanilla, but the Very Hard version (IThieveryRaiseVeryHard.esp) is absolutely ridiculous, and only for people who LOVE to steal.
Skyrim
This mod adds skill requirements to join the College of Winterhold. It is fully voiced because Bethesda planned to have requirements to join the College at one point and recorded lines for being rejected. Also, when Faralda tests your magical prowess, she will test you on your highest skill instead of randomly selecting one of the schools of magic. You can still bypass the test by showing Faralda that you are Dragonborn during the main quest, or with persuasion, just like in vanilla.
The requirements are fully customizable using the MCM. You can set a skill level requirement in one school of magic, and set a requirement for a certain skill level with the other four. You can also set a Magicka and level requirement. I kept a wide range of available values to account for uncappers and 1.9's removal of the level limit.
Increases the number of radiant quests required to advance in the guild, and add skill, level, and time requirements for each of the
guild's milestone story quests.
Current Factions with min requirements:
Mages Guild: All schools of magic require the player to have their skills at level 30 or above
Thieves Guild: Sneak, Lockpicking, and Pickpocketing are all required to be at level 30 or above
In order to trigger the beginning of the Thieves Guild quest, the player must have stolen items, picked pockets, and have some skill in sneak. Otherwise, Brynjolf will not approach you and the dialogue options with him will not appear.
The requirements are as follows:
- Items Stolen >= 250
- Pockets Picked >= 25
- Sneak skill level >= 25
All three requirements must be met.
Beginning in version 1.3, the requirements can now be fully
customized.