You can get a heavy/thick wood stock. Folks used to call them NM (National Match) stocks. Thicker wood is stiffer and resists warping more and it's heavier. It should also have your rifle bedded into the stock with an epoxy compound by an experienced M14 gun smith who knows how to do it right. And then you should only remove the rifle from the stock about once each year for a thorough cleaning and relubing. The stock is better able to resist moisture changes (the cause of warpage) if it's well coated with whatever you choose to refinish it with. Meaning you need the finish inside and outside on the wood surfaces.
The GI synthetic stocks can be stiffened along the forend. Several good threads on it at the M14 Firing Line form. People have used different things to epoxy into the channel to stiffen the forend. Again, if done wrong it can interfere with the rifle function/op rod movement.
Mine had a wood stock on it for about 27 years. I finally put a GI synthetic stock on it several years ago and saw no change in performance (it was never a tack driver anyway). I do like the idea of the synthetic stock being pretty much weather proof.
I put a bipod on mine several years ago. I don't think I'd do that today. A bipod is okay for plinking at a range, or taking single shots, or slow shots. But if you start a rapid fire exercise at targets that vary in range and left/right placement across the range you'll find out a good sling supported firing position is quicker and you won't be fighting the bipod bouncing around.
I used to see GI synthetic stocks at gun shows quite often. The last one I bought was $35 and it was in excellent condition. I bought it because a few tables down another guy was selling them, in worse condition, for $100 each. Look around, keep your eyes open, you'll find what you want. Oh, again, the M14 Firing Line forum has members who sell GI synthetic stocks from time to time.