well my suggestion would make extra coding into forums i think, the developed idea is:
1. Write [import]...[/import] and submit
2. Save thread and make new filed called ImportedID
3. Import text from external domain
4. Handle imported text
5. Save imported text to new mysql database: ID, Importedtext, Updated
View:
1. Open thread
2. Get thread from mysql
3. Check if thread has [import] tags used
4. Get imported text from database acording thread impirtedID
5. Check when was last update of txt file, if not updated in 1 day update database from remote txt file
6. Post mysql saved text to viewer+post imported text (Thread can have normal text + import tags. Allow only one import/thread)
Edit:
1. Get thread from mysql, view original mysql (without replacing [import] tags) text as output and write into quote etc. -> imported text.
Author:
1. When author comes to view thread, allow him yo update threat right away from remote textfile to database
2. Output updated mysql database
If file not found:
1. Use last updated databse stored text.