Is there any possibility to combine line maintenance and light maintenance (containing A, B and C check) under the name of line and light maintenance? In real is there any company which possesses a line maintenance which carried out "A" check and so on?
Line maintenance is activities that can be carried out in the turn around time between flights should something need replaced or repaired.
Although considerably less intensive than D checks, A, B, and C checks can still take anywhere from 8 to 72 hours depending on which one and how many problems. There would not be enough time to perform an A, B, or C check on the line. Not to mention it would cause a huge problem for airports (imagine what sitting on the line for 8 hours for an A check at an airport like ORD would cause), and would cause quite a logistical problem for airlines moving equipment around.
However I would expect that maintenance activities considered "line maintenance possible" will be taken care of when an A, B, C, or D check is accomplished.