If you’re looking for maximum versatility with minimal redundancies, get one premium set of baselayers, one premium set of static insulation, and augment them with cheaper mid layers. It will look something like this:
1) the lightest weight base layer of your choice: poly or merino. A long or short sleeve top, whatever you prefer. Short and long bottoms. Wear this all season, even in winter. This is the most versatile option. In the cold, the light weight fabric means it will retain less sweat walking in as well as dry faster, thus keeping you warmer in the stand. Moisture is the prime enemy. I know you mentioned a set of heavy baselayers but they are very niche. It has got to be very cold to wear something like that through the full range of temps during the day and move around. You can’t shed them, they hold more moisture due to more fabric mass, and no matter what anyone says, even the heaviest base layers do not have a high R value. Don’t think of them as insulation.
If you’re dead set on a heavy baselayer in the rotation too, get a top and bottom set of ECWCS level 2 surplus gridded fleece off eBay and wear it next to skin. Cheap, fantastic moisture management, and they can double as midlayers. I personally can’t wear these next to skin in temps above 20. Just too warm.
2) midlayer tops. This is where you will get your versatility. Fleece is fleece and it’s the cheapest layer by far. Get a few different weights that will fit your expected temps and activity. There’s very little reason to buy expensive fleece. You could buy 3 tops for the price of one merino baselayer top, so use this to your advantage. You can find generic classic 100, 200, or 300 weights at any thrift store. Also with a little knowledge of what to look for in fabric design, you can even find some premium polartec (or a copy thereof) power grid, high loft, or power stretch at great prices. Again, ECWCS military surplus level 2 grid fleece make great midlayers, as well as the level 3 high loft jacket. Both can be found on eBay. Basically lower QC Patagonia (and some early runs were made by Patagonia).
3) Any durable pant of your choice that won’t retain moisture (likely nylon), can stand up to brush/thorns, and that you could comfortably hike around in from 70 to 20 degrees (don’t worry about insulation, that’s the next step).
4) IMO It would be worth it to find a lightweight wind breaker. 5oz and they pack down to nothing. Pair this with your fleece midlayer for wind proofing without paying a premium for a membrane and retaining the versatility of two separate layers. A heavy fleece like a fluffy high loft and wind breaker is likely all you’d need for static insulation in the fall. Only cons, keep it away from thorns, and the nylon can be noisy, so it’s personal preference whether you feel you’d like this layer for whitetail. If you set your platform/saddle 5 sticks high, it probably won’t matter. If you hunt low, might be an issue.
5) Finally, get dedicated static insulation top and bottoms that you can just slide over all existing layers when you reach your ambush point. You will not be moving in this, so it doesn’t need to breath (ie windproof), and it be better to go for a lot of insulation. If it’s too much warmth on stand/saddle, shed your midlayer. Down or synthetic puffies will be the warmest but like the windbreaker, their nylon face fabric can be noisy and fragile. Another option would be some specialized whitetail centric system that forgoes packability in exchange for a silent construction, like the Sitka fanatic. For budget bottoms, quilt lined carhartt bibs will get you 90% of the way there especially if you’re only breaking them out in the 20s and any moisture that could wet the canvas will always be frozen. Budget puffy bottoms would be the ECWCS level 7s. Also, if you can find some booties that slip over your shoes/boots that will help too. At least for me, my feet are always the first thing to start getting cold when I’m static. This also means you could wear less extreme footwear hiking in for those days the temperature swings widely from dawn to dusk.
For the surplus stuff, go one size smaller than your normal size.
