I have just found a solution that seems to be fine for me, so I want to share this with you here.

As it is now, AVCHD is just another compression algorith my camera uses to save space and maintain a decent quality.
When shooting, I can change between interlaced and progressive scan, and I have so far mostly tested it with interlaced. Interlaced looks way better on my PC, and definitely on the camera itself when shooting, the question is how it will look an a TV when I am done with my "production".

As soon as I have transported the footages to my PC, I follow this approach:
How to edit AVCHD M2TS files
I use the VirtualDubMod combined with the Smart Deinterlacer Filter and the built in deinterlacer, in this order.
I then save to AVI using the Cineform codec, or the XVID (smaller files).

As it looks now, VirtualDubMod is way faster than Vegas for this particular job. I will now use high quality Cineform (or XVID) AVI files in Vegas, and see if I can do without proxy files.
If anyone has any objections <g> I will be more than happy to know!

Ingvarai