Here's is my theory for a plot synopsis to introduce AK's character to 2.5 men. (FWIW< lol!)
Charlie will travel abroad to pursue Rose, who has disappeared. Ashton will portray Rose's free spirited brother who is looking for the missing Rose. He will not live in the Harper home but in the family home (Rose's family) but is connected to the Harpers thru the absence of Rose and Charlie. He will be a central character who is quirky, like Rose, and climbs over the deck to insert himself into the Harper home. (His character will be similar to Kramer on Seinfeld,IMO) Jake will adolize AK's character, which will drive Alan crazy!
The writers know that Jake is growing up and should move the plot towards the next stage of his life. My feeling is that we will see the torch being passed, so to speak. In the past, we have witnessed Charlie's and Alan's shenanigans. I think we will now see Jake (Angus T, Jones) and Ak's character engage in shenanigans.
I think AK will bring a fresh comedic relief to the show (which had become somewhat stale, IMO) with a good script. I wish him well. (No offense intended toward Jon Cryer or Angus T. Jones because they are the reason I watch the show)
I wish CS well too...but it is time for him to move on. Moo, but he has some important issues to confront.
It will be interesting to see how it plays out to say the least.
MOO
wm