My only input is that I think wetsuit skins are a poor choice for use under a drysuit.
I think the most important property of a drysuit undergarment, other than how well it insulates, is how well it wicks moisture away from your skin. A nice, warm, thick undergarment will not feel warm if your base layer is holding moisture against your skin. Wetsuit skins generally do not breathe or wick. Under a drysuit, they will most likely make you sweat a bit and hold that moisture against your skin.
I have a large pile of Lavacore gear that I bought when I started diving. I had the same basic train of thought as you. After the first few months, I have never worn any of it again.
I think the most important property of a drysuit undergarment, other than how well it insulates, is how well it wicks moisture away from your skin. A nice, warm, thick undergarment will not feel warm if your base layer is holding moisture against your skin. Wetsuit skins generally do not breathe or wick. Under a drysuit, they will most likely make you sweat a bit and hold that moisture against your skin.
I have a large pile of Lavacore gear that I bought when I started diving. I had the same basic train of thought as you. After the first few months, I have never worn any of it again.