Hi bbinspace,
I'm not sure if i understand the question fully. As you won't be able to Sync Ableton to any software that works with the DDJS1 however,
You can midi map the APC40 in Serato DJ -
serato.com
Serato DJ is a free upgrade for the Pioneer DDJS1 that allows you to midi map various functions in Serato DJ to the APC40 :)
Here's our guide on mapping in Serato DJ -
serato.com
Hope that helps :)
Matt P