I just finished an Ascension-SCS solo run on BG2EE with the Big Picture mod and Oversight (Sendai) installed. BP-Ascension is currently the only way to install Ascension, as @Cuv
's version is not ready yet. I can verify that it runs mostly well, except for two instances: when I was fighting Sendai (Enclave Fight) and the Five (Final Fight).
When I was fighting Sendai, I couldn't get her to launch her death script after going through her statues and bringing her to Near Death over multiple instances. I eventually moved on by doing the Shapeshift-Mindflayer trick, which killed her and started the Pocket Plane cutscene.
The second glitch was when I fought the Final Five and I couldn't get Abazigal to launch his death script. Every time I brought him to Near Death, he would change into... Irenicus! And the fight could not be finished because Melissan can only be killed after all of the Five have launched their death scripts. For this glitch, I had to go into the script for Abazigal (using Near Infinity) and found that he was missing a death script, but instead had a strange script which transformed him into Irenicus. So I copied Yaga's death script with some appropriate changes and replaced the Irenicus portion as below:
ReallyForceSpellDeadRES("melspl10","finmel01") // Feedback
That solved the glitch. Was able to deal with the Five, save Balthazar from Near Death, and finally bring Melissan down. Took my four years to get around to finishing Ascension, but I finally did it. Whew!
After this, I took a look at the Sendai script and noticed it was missing a death script. Haven't replayed that part yet, but I intend to insert a death script from Abazigal (Enclave) into her script and hope it works:
Anyway, all's good and I just wanted to share my experience with others in case they come across the same glitches.