the Great windows app Avisynth works fine on Linux (under wine) and they are in the middle or porting it right now.
On windows I used to use Adobe Premiere because it could open avisynth scripts (using a plugin) - which meant I could do all kinds of adjustments and also open files types that Premiere would not ordinarily be able to open. Not many video apps support avisynth scrpt which is a great pity as it is so useful.

The AVXSynth devs are going to add .avs support to FFmpeg for Linux at some point, which I created a thread about here but no response and that I'd imagine is the first step towards MLT exposing that FFmpeg support for kdenlive.

is it possible to implement something like this?
http://avsfilter.berlios.de/req_compile_download.html

may be as Frei0r plugin...

It would need doing in MLT the under lying media framework and the avsfilter thing looks a bit of a fudge, requiring Wine etc. AvxSynth a native Linux Avisynth is in the making, better to implement that assuming there's a dev interested enough or free to do it. :-)