Many borders don't reflect the ethnic, religious or cultural majorities and are perpetual suspects whenever some conflict flares up. The Sykes-Picot Agreement is under much criticism nowadays, and the borders in all of Africa appear to be just as artificial. The conflicts in Nigeria and Mali can be considered to be consequences of borders which don't reflect the cultural divide between the Tuareg and other Muslim minorities in the North and the Southerners, which tended to have been more under European influence (religion, language) due to easier access from the coast.
A repair of such nonsense borders may indeed avoid future wars, but I doubt it would be better than a 85% solution. The problem is in many places the very same as it was in Bosnia - no sensible borders could be drawn because of chaotic dispersion of ethnic or religious groups.
|Bosnian ethnic map 1991 (c) "Milan1237"|
Radical changes of borders are furthermore very, very difficult and usually possible only through war because the governments have vested interests in the status quo.
The long-term solution to the problem of poorly devised borders needs to be a different one. The most obvious solution would probably be the best one as well: Make borders irrelevant; shared sovereignty over territory.
This isn't without precedent at all. The feudal societies of (at least) Central Europe had well-defined borders between the upper levels, but at the lower levels, lower nobility and monastries, the "territory" of these princes was actually defines by individual farms. There was no cohesive territory - the realm of a monastry or a lower prince consisted of a collection of ownership deeds for specific farms.
Likewise, a modern state could be defined not by a territory, but by what matters for real; its citizens. The state would be where the citizen lives - within limits, of course. A region such as Bosnia could be home to three states with three governments - but without simplistic borders. The sovereignty would rather be dependent on circumstances instead of by geographic location. Similar to how the authority of different law enforcement agencies would be dependent on what crime happens and what criminal code paragraph was violated - rather than by geographic division.
The private and legal (economic) interaction of citizens or government agencies of different such states would require specific rules, but those could be set bilaterally just as already done with interactions across borders.
The intriguing thing about such states with shared territorial sovereignty is that despite their outlandish appearance, the powers that be would actually lose less if anything and might be more ready to accept such a system than radical adjustments of borders. The scattering of ethnic groups which makes border corrections utterly impractical in many cold conflicts would probably even make such states with shared territorial sovereignty more practical, rather than less.
An alternative is the model of the European Union, of course - the integration into a multi-ethnic super-state and government. This helps to some degree, but I doubt it has much potential beyond the degree of integration as realised in the EU already. The (perceived) costs of further integration appear to outweigh the benefits - particularly as long as language barriers and very much different perceptions of policy and politics persist (because of separated mass news media).