But the work of migrating software to a non-1541 kind of drive has already been taken care of. Look for software modified to run on the sd2iec or the 1581.
Also if I take a look around at demoparties, I didn't see anyone using a disk drive any more. 1541-ultimate or Chameleon are used with disk images. Even for the the C128 with burst mode there is a patched version of the sd2iec for that.
“Nobody knows wether the C65 supports the burst mode of the 1571?”
Sure we do. Take a look at: https://github.com/MEGA65/c65-specifications/blob/master/c65manualupdated.txt
The chapters starting at lines 13586 and 13657 state the burst load exists, but burst save doesn't.
Nevertheless, I can see the desire for wanting JiffyDOS or something alike. (I'm asking for parallel cable support in the Chameleon constantly, to get SpeedDOS/DolphinDOS running.) But this should be something that can be taken care of as a community effort after the release. Something like a github-repo containing different flavours of the firmware, as there are a lot of ways the kernal can go, as the mass of patched C64 kernals shows...