If Allure supports the Cucumber JSON output it should work. Else suggest you take this up with the Allure team.
You can refer to this thread (for Extent): https://github.com/intuit/karate/issues/619
EDIT: Since I refer anyone asking about extending / custom reports to this answer, read on.
In Karate 1.0 onwards, the Results
object can be used to get all data about the test results. Also multiple JSON files will be output to the <build>/karate-reports
. You can even re-try some tests and merge the results: https://github.com/intuit/karate/wiki/1.0-upgrade-guide#retry-framework-experimental
Also please be aware of changes to the Java hooks, it is called RuntimeHook
now: https://github.com/intuit/karate/wiki/1.0-upgrade-guide#hooks