The other thing with Kryptonite Woman was that as I said it wasn't even necessary...they'd ALREADY written out Kristen with the video diary! That was a perfect ending given what they'd established with Lana's personality and how she does things. All her return did was slow things down between Clark and Lois which started to finally heat up. Personally I think as I said they wanted to give Kristen a "Good" departure...from interviews that Kristen gave in the Vancouver Sun at the time it seemed like she really was tired of the role and had no intention of returning at all.
Regarding Alicia and Chloe...I always looked at that as Alicia's last good act. She was giving Clark a gift in a way...that gift was Chloe, one of his closest and best friends learning and sharing his secret. I thought it was Alicia in her own kooky way giving what she knew Clark needed.
Plus knowing how the Smallville writers wrote...it probably would've been another season and a half before Chloe figured it out on her own LOL.