Why is it that both the base to mid Ford and RAM Trims have better seats, offer Fog Lights and more choices of Gear Ratios??? The Custom trim is not much of a step up from the W/T yet Chevy wastes (2) trim levels on it and the LT Trim is a joke compared to what it was.
As you point out, de-contenting the high volume models WILL HURT sales, so it is no surprise that Ford and RAM are selling better, and those "New to Brand" buyers are likely to "move up" on their next purchase, so GM is losing current customers of lower priced trucks today and will lose a high percentage of those same customers of high priced trucks in the future.
You are correct about the transmissions, there is no reason for the 5.3L not to have the 10 Speed and the base transmission has to be upgraded to the 8-speed.
Totally agree that the 5.3L must be offered with the 10 speed and the 6.2L should be offered on all GMC trims and be offered on at least the LT trim level for Chevrolet.
No reason the 4.3L and 5.3L on WT trims should not have the 8-speed, the Express/Savana have had the 4.3L with 8-speed for 2 years and they are "Commercial Fleet" vehicles so it should be the same on Silverado/Sierra.
Gearing is another problem area, the Trail Boss and AT4 have to offer 3.73 gears and it should be available on all Off Road packages like the Z71, this is an easy fix.
Another easy fix is replace the low feature/low comfort seats with seats from higher trim levels, at least that would make lower end (high sales volume) trims more attractive to buyers. GM can have a competitive interior at the low to mid level trims at least by changing where features/seating are offered. The top end trims just have to get new interiors ASAP.