QuickLoad or a similar reloading program could be your friend here. You're talking about potentially significant trade-offs...increased velocity to keep the heavy bullets supersonic and/or stable out to those distances versus increased barrel stiffness/precision/resistance to heating and POI shifts. QuickLoad would allow you to make some reasonable estimates of velocity/pressure with differing barrel lengths and your bullet/powder of choice.
The real question in my mind would be how short could you actually go in terms of minimal barrel length when trying to lob heavy .308 bullets out to 1000-1500 yd and still realistically retain sufficient velocity for stability and precision. QL would be ideal for addressing this question. Once you know that answer, you can then determine how much weight savings the shorter barrel would represent, and how much heavier a contour it might buy you.
Unless the flutes in these 32"-34" barrels others are currently using are ridiculously deep, the weight savings as a percentage of the total barrel weight probably aren't that large. If that is the case, another possibility worth consideration might be a compromise of the two extremes you listed. That is, a barrel length of 28"-30" either simply without any flutes necessary to make weight, and/or just a slightly heavier contour...i.e. just enough to provide some extra stiffness, but still make weight. The concerns about velocity/pressure would be somewhat less in that scenario as compared to a heavier barrel in the 24"-28" length range.
My primary thinking here is simply that barrel stiffness doesn't buy you any velocity. So having a good estimate of how short the barrel can be and still provide the necessary velocity at safe operating pressure would be the place to start. Once you have some idea of that answer, figuring out approximately what that barrel length buys you in terms of weight savings heavier contours is relatively simple. QL might be of benefit in addressing that critical question. It's also worth mention that barrel length alone is not the sole variable in this equation in terms of velocity/pressure...it's also at what velocity/pressure a barrel of given length will tune in with a particular bullet/powder combination. Just because you can achieve a certain velocity with a certain length barrel doesn't necessarily mean that the load will tune in well at that velocity. QL can also help with predictions of that sort.
Finally, it is unclear to me exactly how much a heavier contour barrel really buys you. Obviously, when comparing extremes such as a straight contour versus a pencil barrel, the differences are pretty easy to anticipate. Comparisons of [closer] contours in between might be harder to differentiate. I have 30" barrels on different .308 Win F-TR rifles ranging from Heavy Palma to MTU to Heavy Varmint with a 1.35" shank. In fairness, all three of these contours would be considered relatively heavy. However, in both a relative sense and in actual weight, the HV barrels with the 1.35" shank are a much heavier contour than the Heavy Palma. Nonetheless, the Heavy Palma contour barrel is more than heavy enough to shoot just as well in my hands as the others over the relatively long (25+ shots) strings of fire in F-TR. Lots of F-TR trophies have been won by people using Heavy Palma contour barrels, so they obviously work well. Along the same line, the MTU contour barrels have a little more weight out front, which I like, but not everyone does. So it's not solely the barrel weight/stiffness, how that weight is distributed may also be a consideration. Notably, the Palma contour barrels have a curved taper and thus become thinner very rapidly after the straight contour at the breech end, meaning the front two-thirds of a Heavy Palma contour barrel will be noticeably thinner than an MTU barrel of the same length. The HP contour barrel will also be substantially lighter at a given length for the same reason. So in terms of figuring out how to save some weight in order to gain barrel stiffness, you may need to consider not only length, but how that weight is distributed in various barrel contours. Along this line, a call to a reputable barrel manufacturer may be of benefit. If you explain what you're trying to do, they can probably help you if anyone can.
