Kerbal Space Program

Note: In the interest of brevity and to make this easier to understand, I'll be jointly referring to fuel lines and struts simply as "lines".

There are a few issues in current versions of KSP which can make the use of lines frustrating and difficult to learn.

1. When placing lines, the secondary end does not snap to the grid. This can make placement very difficult, and with struts it can cause stability problems.
2. Regardless of the secondary end, if the line intersects another part it becomes attached to it. The editor, however, always shows the line as complete before you click to place the secondary end, which is misleading.
3. It isn't possible to move the ends independent of one another. When moving a line, it's much more common to move just one end, rather than both. It becomes especially frustrating when the line is in a difficult-to-place position, like between two closely-spaced fuel tanks.
4. Moving the part to which the fuel line or stut is attached can cause unpredictable and unexpected results. Most often this means the line will simply not be connected any more, which is likely to be overlooked. Other times it will connect to a different part than what you intended, which can be especially problematic for fuel lines as the cause of fuel flow problems would be difficult to determine.

I propose a solution to all of these issues: storing both ends of the line as a separate part which share a unique identifier. Instead of basing the position of the secondary end by calculating where the line first intersects with another part, KSP would simply use the other part. In the editor you could use that same intersection code to validate part placement – if the line intersects another part it will show as unplaceable.