Does he break game balance or no?
What to expect a character like this to do?
I have a player asking to play one but i dunno if it will become a trouble in the future
As the DM, you can restrict the spell access by deciding which scrolls he can and can't get easily.
An Archivist makes a great hook for adventures: old abandoned temple to a forgotten god- he's there, strange esoteric cult - better believe he's there etc.
DM’s Power
Before you decide to play an Archivist, there are some questions you will want answered about the campaign. Here are some of them you will want to ask:
Q: What material will be allowed in this campaign?
An archivist, more than almost any other class, has a power level that is directly proportional to how many options are allowed in the campaign. The more divine spells there are, the wider your spell list is. Here are a list of thing that if allowed, will affect your power:
• Adepts – This NPC class gives access to some divine spells earlier than most PC classes.
• Any sort of cheap trick to get any Sorcerer/Wizard spell as a divine spell – I’m not talking about domains that grant wizard spells as divine spells, but class features that allow virtually any Sorcerer/Wizard spell as a divine spell. Some examples of this include Divine Magician variant, Hexer PrC, and Favored Souls of Bahamut/Tiamat.
• Divine Bard – This variant found in Unearthed Arcana or the online SRD allows you to add any bard spell to the spell list.
• Warlock or Pre-errata Artificers – Level 12 Warlocks or Pre-errata Artificers can create any divine spell in the game. A PC like that in your party can be a valuable asset to your Archivist.
• Any non-core divine casting class – Shugenja, Favoured Soul, Healer, and Spirit Shaman for example.
• Divine Prestige Classes that add more spells to the class’s spell list.
• Any Domains – According to Sage Advice, divine spells from domains are fine.
Q: How does buying items work in this campaign?
In some campaigns, buying an obscure scroll is as easy as a trip to the supermarket. In other campaigns, there might not be a lot of some of the more obscure classes running around or making scrolls. It might be worth it to invest ranks in gather information just because of this scenario.
Q: Should you be worried about terrible things happening to your prayer book?
This is more a question you should ask yourself (no reason to give your DM any ideas). Maybe investing in some sort of failsafe system would be a good idea (More ideas welcome).
my suggestion is to 1st take a look at that thread and 2nd consider the maturity of the player asked u to do that: i think that between mature ppl there's no reason to prohibit potentially game-breaking choices, if the player in question is wise he will know that braking the game will lead to nothing else that boredom for everyone
just my 2 cents
I shall give the guy a chance.
i should PM him first about the matter;
I've seen a bunch of people use a home-brewed feat called "collegiate archivist" based off the "collegiate wizard" feat to help pump up spells known. People also like to play Illumian archivists for their bonus to intelligence-based skill checks and for their ability to switch the bonus-spell stat to something like dexterity. Both of these improve the situation somewhat.
I played an archivist in a game where the DM was just not offering many scrolls overall and few if any scrolls from off the cleric list.
I quickly got frustrated and switched to a cloistered cleric with knowledge devotion and the divine magician alternative class feature from complete mage. That captured the feel of the archivist quite nicely and eased tension between the DM and me.