World X is imperfect.
We live in world X.
God is perfect.
We achieve perfection through process Y, created by God to bridge the gap from our world to his.
This entire feat (world X, process Y, salvation...) is part of a perfect plan whereby world X was simply a required constituant of this plan.
The creation of an imperfect world to accomplish a perfect motive is fully perfect and practical.
Small picture (our world) - imperfect
Big picture (overall plan) - perfect, but includes imperfect small picture
However, you pretty much said this in your post correct? At least I may have summarized it in my own words...
Take this as an example that has nothing to do with God and salvation but nonetheless conceptualy relates indirectly to the topic at hand.
You build a model-T Ford which sucks, but its the best you can do and it gets the job done. On down the line we get hybrid gas/electric motors with low emissions, fully loaded with luxury interior and computerized navgational and safety equipment.
The model-T is imperfect, the 2004 computerized cars are still imperfect but improved, the 2010 models will be closer to whatever a "perfect car" is, but nevertheless not perfect. It's not the cars that are perfect and they were never meant to be. They're only meant to be better than last years model. This process of improvement never faulters and never moves backward-only forward toward perfection. It is not the cars that ae perfect; the process of improvement is what's perfect. The plan is to improve, and the plan doesn't faulter (we'll never go back to a model-T). It's a process of which each imperfect vehicle has its place and plays a vital role (that is to be studied and improved upon, as well as provide convenient transportation at an affordable cost).
So the cars are each imperfect but they serve their purpose in the overall plan.
Our world is imperfect but it serves its purpose in a perfect plan. You may even say our world appears to be getting worse, not better (like the cars are). But perhaps the perfect plan of salvation requires a world that slips more and more into imperfection. (Worser and worser road/environmental conditions inspire more drastic auto improvements - lower emissions, cleaner fuel, more miles to gallon, higher impact safety features, improved traction & handling, etc.) This is not to say that the people of today are better than the people of yesterday because the world is worse off (actualy, thinking of midevil Europe's dark ages, the world being "worse off" would appear to be a false statement), but this is merely to say that the appearance of imperfection is simply a required piece of a bigger picture.