If you want less legacy, try Hollywood 6.0. It has so little legacy that it currently doesn't support the Amiga chipsets at all!
A friend and I tried to make a new compiler as a sequel for Amos codenamed "Mattathias" that would support custom operators and be able to build extensions for itself. It would be basically a self compiled Ruby substitute. The two of us could not finish it even though we tried for 8 years. Thankfully we now have access to the AmosPro source code so we don't have to try that again!