I'm not going to deny that choosing countries has every potential to have early negotiating, but I think with those that agree that negotiation before a game even starts is bad, you won't have to worry about that kind of cheating pre-game or in-game.
Now with that said, I believe someone said that no matter how many precautions and safety measures are taken, if people want to cheat, they will find a way to cheat. I believe the purpose behind the choose option is so that those who wish to create tournaments where you might need to have specific country selection or for those who play regular games with others can have different set ups (like the same 7 people playing games as different countries). True, they could just have the computer choose randomly, but the option is there to have a certain measure of control. My question in this situation is: are these people cheating because they are playing the same 6 people (or however many people depending on the map)?
In general, I tend to agree with your assessment and comparison between "quality" and "feel good." I think you are mostly spot on with this idea. The only thing I would add to this idea is the "feel good" concept applies to all games, not just ones that you choose your countries, because if that were not the case, we would have no (or very few) NMRs. These concepts are across the board, and as such, I do not believe they have any place in this argument.
Furthermore, this site was created (to the best of my knowledge) to be a place where different maps could be played instead of just the original 7-player map. We have maps for 2 players, 3 players, 4 players, and on up. There are many options and features that are intended to make the game a custom experience. If you want to play games where people's countries are randomly selected, pick that option. Don't join a game, lose, and then complain because you thought they were cheating. If they want to cheat, then let them cheat. Take down there name, block them (handy feature, isn't it?), and don't play games with them. Only play games with people who you can trust will uphold the integrity of the game and play with/against them.
I came to this site from webDip because there were so many other options of things to do with the game concept of diplomacy. The 1v1's I call "tactical diplomacy". Gunboats, I still consider diplomacy because you can communicate through your moves. I play only what I want to play. You have the ability to. So exercise that ability and please stop arguing about a feature that only might encourage cheating.