Here is my (cynical) view:
https://www.law.cornell.edu/cfr/text/14/121.43
135 PIC counts for nothing unless it’s 10+ seats or commuter operations aka “scheduled 135”.
I don’t see how 135 PIC time on your average rent-a-jet would do him any favors.
I have 135 PIC jet time and it’s has done zero for me.
I used to fly with somebody from the Regionals and he went 135 for the exact reasons He mentioned and last time I saw him he was still there.
Couldn’t handle the $30k+ pay cut it to go back to first year 121.
Your friend is 121, stay there.
No 135 that I know off will put you in the left seat on day 1,
You’ll spend a year right seat.
So you’re not gaining anything.