And the more I think about it, the more I think this is a WORSE experience for customers than a straight implementation of E+ on AS would be. You're taking away seats from MVP/MVPG customers they used to get for free, and that's NEVER popular (witness grumbling about baggage fees). Sure, you can sit in the back of the bus if you don't want to pay... but then you're going to get things like MVPGs who fly a lot on AS who pick a seat assignment without paying for "North of Coach" getting a worse seat than a smart FTer who
doesn't fly AS very often, but knows from how E+ works on UA that if she doesn't pick a seat, she has a good chance of being put in a North of Coach seat at the last minute for her seat assignment. That's just kind of South of Expected- you're rewarding the person who knows how to game the system, not the loyal customer.
Also:
I would tune the pricing of this product (North of Coach) such that it typically didn't sell out weeks in advance, but rather that seats were usually available fairly close to the date of the flight.
...which means you have a non-zero risk of NOT selling the ticket, and having lovely empty seats that have great room in coach that would have sold, had you not decided to price them so high.
Also, you're going to hurt F sales by offering an intermediate Y+ product with additional leg room + drinks + digEplayer + food. Basically, you've just replicated F on a 738 without as wide a seat. 738 F for AS is 36-37" pitch, per seatguru- in fact, some Y seats (Row 15) have better pitch than some F seats on that plane.
The reason why VX can offer Main Cabin Select and First is because VX F is much closer to AA Flagship Service F and UA p.s. (both of which are
3-class F) than a standard domestic F like AS has- the pitch is a lot deeper and the VX F seat is MUCH nicer than anything AS has. This means you can offer MCS and not cannibalize F, because there's very clear product differentiation (F gets recliners, different food, plus the usual F cabin stuff), plus VX does a lot more BOB than AS does (all AS does is ONE menu item + snack packs). Your "North of Coach" product is going to either cannibalize F customers, or require you to do something like increase F pitch and services to clearly distinguish between Y+ and F, which will add costs (and if you have to rip out F seats to get that extra pitch, potentially decrease revenue).