The reference to fleece undergarment reminds of the at least decade old fad of plush lined suits. They were comfy but the plush lining allowed for more water flow and they really were not any warmer.
You can find 2mm or 3 mm neoprene socks in most sporting good stores and they do work well under a 7mm bootie and add minimal bulk. They also make good dry suit socks.
Scubapro used to sell 7mm gloves and 3 finger mits with a smooth rubber inner sear and a smooth inner faced out seal. This matched a similar smooth rubber seal on the wetsuit sleave and when stacked properly prevented most of the water flow into either the glove or the sleave of the wetsuit.
Failing the continued availability of something similar to this, a longer gauntlet type glove minimizes water flow and a three finger mit keeps your hand warmer overall than a 5 finger glove although you have all the dexterity of the invading alien in a bad '50's sci-fi movie.
I have a pair of Deep See 5mm titanium gloves and they work very well. They have this smooth titanium lining that frankly does not reflect anything despite what the markrting folks say. But it does make for a very smooth inner surface. The gloves fit closely and the smooth inner surface allows less water flow than a similar nylon lined neoprene glove. The gloves are also well cut with pre-bent fingers and fit my hands well which is a big part of warmth in a glove. If there are spaces and pockets inside the glove when you are wearing them, they will pump water in and out of the glove every time you move your hand no matter how well they are sealed.
A "cheater" hood is also useful. These are a 7mm hood with a 3mm to 5mm vest attached. It adds another layer under the wetsuit or semi-dry and also inhibits water flow through the neck and adds another layer of coverage over the wetsuit/semi-dry zipper whether it's on the front or back. They are available with or without a smooth neoprene "seal" area to fit against the smooth neoprene neck seal on a semi-dry suit.
When it gets too hot to comfortably don my drysuit (most days after early June), I use a Scubamax one piece 7mm semi-dry with an Akona 3mm/7mm cheater hood, 7mm boots and the above mentioned 5mm gloves in water down to 40 degrees at the bottom for up to half an hour or so and am comfortable as long as the deco is above a thermocline and closer to 60 degrees or so.
There is a lot to be said for a drysuit and I own two, but I still prefer a wet suit or semi-dry when practical as they are less bulky and offer less drag in the water. I also don't get overheated putting one on when it's 90 degrees out.