From the author jastey:
I feel under a lot of time pressure every time after the incident with Irenicus, Imoen, and the Cowled Wizards at the Promenade. This mod lets Imoen be turned to stone in that fight. The idea is to give the PC more ease of mind to do all the quests in Chapter 2, knowing that Imoen doesn't suffer - and can be turned back to live like Branwen was in BG1 once the PC reaches Spellhold.
The mod lets Imoen be turned to stone in the fight with Irenicus at the Promenade. She will still be taken by the Cowled Wizards, and Irenicus will have depetrified her and do his soul-experiments until the PC reaches Spellhold so the overall game flow is not altered. But overall it all happens a bit later than in the original, and (at least for me) it's a bit less disturbing.
This mod is meant to be a very small mod, which is also one of the reasons why the overall game story is not altered.
The mod tries to use as many originally voiced lines as possible, but some had to be taken out because they didn't make any sense without Imoen reacting. Also, some lines were added to stress the reasons why Imoen will be taken to Spellhold although she is turned to stone.