the editors i work with like to use FCP's Speed effect for speed manipulation and ramps because they can get their ideas down fast and move on. the editors have tried to use Twixtor in FCP, but it can really slow them down (and some just prefer using FCP's Speed effect even though it looks awful, and have me fix it later). i then take their edit and use Twixtor in either FCP or After Effects to copy the basic idea of their speed changes and ramps, because it looks much better than what FCP can do on its own. i'm wondering, is there a way i can copy the speed changes using FCP's Speed effect over to Twixtor in FCP or AE, instead of trying to do it by eye? i've tried using Automatic Duck and Boris XML tool for the FCP to AE import, but they don't read the FCP speed correctly. it will usually read speed ramps as only a few keyframes (ignoring FCP smooth ramp feature) or keyframing every single frame, which doesn't allow Twixtor to do its inter-frame creation magic.
I've just contacted Automatic Duck to ask them about why their speed changes aren't converted to AE properly. If that works, or we can get them to fix any problem, then that's a very good way to do it.
What version of Automatic Duck's product are you using?
Ah, here's another thing I didn't see in your original post:
You said Automatic DUck or Boris XML Tool can work by " keyframing every single frame"
if that's the case, then you are in luck.
I presume the tool that keyframes every frame does so by applying After Effects Time Remapping?
if so place Twixtor on the clip in a precomp (let's call it PRECOMP).... leave the speed setting at 100%. Then put this in another comp (let's call this FINAL COMP) and copy the timing curve that Automatic Duck or Boris XML creates on the footage you are retiming to a time remap curve you create within the FINAL COMP.
In this way you can use AE to control the retiming curve (which comes from FCP), but use Twixtor "under the hood" to create the retimed footage.
So you project would look something like this:
PRECOMP: inside this you have your original footage. Twixtor is applied with 100% speed. (don't worry we'll retime this in the second comp).
FINAL COMP: inside it is PRECOMP, and the time remapping curve is the one that is frame-by-frame that you had translated from FCP.
If you have trouble with this after you import a timing curve from FCP into an AE project, let us know and we can help further. Send a sample project (with timing curve) to techsupport (at) revisionfx (dot) com. No need to send media.