Is "as" used as pronoun in "Such....as" in sentences?

Here in below a sentence from 'Word power made easy Norman lewis' book.

The church proscribes, or announces a proscription (pro-SKRIP-shon) against, such activities as may harm its parishioners.

In sentence above, could "as" be replaced with "that". If so, then it seems to me that "as" functions like a pronoun (But as far as I know, "as" is not used as pronoun).

Is grammatically correct the use of 'as' in above sentence? If not, then what is the right structure? If yes, then why it is correct? Please explain!!!

In above sentence, could "as" be replaced with "that".If so, then it seem to me that "as" working as pronoun(But as far as I know, "as" is not used as pronoun).

Here is the explanation of the
"such _ _ as" construction (Reference Collins dictionary)

1. Function of "as":.
   In this sentence, "as" is not a pronoun; it functions as a conjunction introducing a descriptive clause ("may harm its parishioners") that specifies the type of activities.
2. "Such...as" Construction:.
   According to the Collins Dictionary, "such...as" links a noun (modified by "such") to a clause introduced by "as", which describes or specifies the kind of thing or person being referred to.
3. Role of "such":.
   In the sentence, "such" is a determiner that modifies the noun "activities", specifying which activities are being referred to (those that may harm parishioners).
4. Comparison to "such...that" sentence:.
   While "such...as" specifies or categorizes, "such...that" expresses cause and result. Example: He was such a good teacher that we all passed the exam..
   Here, "such" functions as an intensifier, and "such...that" works as a correlative conjunction linking cause and result.

II. Supporting Reference:.
"Such...as" from Collins Dictionary:

such - determiner meaning.
You use such...as to link something or someone with a clause in which you give a description of the kind of thing or person that you mean.

• Each member of the alliance agrees to take such action as it deems necessary.
• Britain is not enjoying such prosperity as it was in the mid-1980s