This talk of "streamlining" the game by reducing the number of missions makes me nervous. I find the idea of only 30-40 missions in a game really unsatisfying: I enjoy a long, grueling campaign with many missions, slow tech advance, and the need to gradually build a large, global organization with multiple combat teams spread around the world. To some people this seems tedious, to me (and others I'm sure) this is exactly the heart of the game. I do every crash site because that's what I enjoy, not because I need to obsessively maximize benefits. Ideally you could build in options to cater to the range of playing styles, perhaps along the lines of Civ's "Marathon, Epic, Normal, etc" options where you can choose the pace of progress in the game.
For example, a fast-paced option would have faster invasion progression and tech advance rate, fewer UFOs (thus fewer crash sites) but more gain per recovery in terms of salvage and soldier advancement. For the slow-paced option, the opposite.
Reiterating earlier posts, there are more elegant ways to limit number of crash missions without autoresolve.
1. Increase the % that a UFO crash is a total loss, nothing recoverable.
2. Make the ability to do every mission offset by the costs of building the infrastructure needed to do so. In other words, with a "minimal" set-up of 1-2 combat teams, I couldn't do all the mission if I wanted to, but with 3-4 teams the extra cost eats up the gains from extra missions. I personally would enjoy the latter, even if there were no net gain in "game progress". Some ways to do this:
2a. Decrease the time window that crash sites are available. As it is, I can send a team from halfway around the world. If they disappear more quickly, I'll need more teams spread around the world to reach every site in time, and this might offset the benefits of trying to reach each and every site. As it is, I also usually have the luxury to delay sending a team until daytime. If I was pressed to send a team more quickly, I might pass on night missions because I'd perceive the cost as outweighing the gain.
2b. Impose a recovery time for soldiers - some period of R&R before they're ready for a new mission. This way I need a larger pool of soldiers to draw on. I might not consider it worth doing every mission given the extra cost and the fact the gains are being watered down by distributing them over a wide group and not a single team of main soldiers.
Also, let me cast a positive vote for the idea of "mixing up" the crew composition of scouts to deal with they same-y-ness.