Cannot easily/safely catch exceptions without disrupting job abortion

onErrorMarkUnstable("sleep step") {
    // stopping here raises FlowInterruptedException
    sleep 10
}

onErrorMarkUnstable("sleep shell") {
    node {
        // error here raises AbortException, stopping here raises AbortException

        // a script that fails.. we want to be able to log that it failed and continue testing.
        sh "sleep 10 && false"
    }
}

onErrorMarkUnstable("sleep shell with timeout") {
    // we want to log that it timed out and continue.
    timeout (time: 5, unit: 'SECONDS')  {
        node {
            // error here raises AbortException, stopping here raises AbortException, timeout raises FlowInterruptedException
            sh "sleep 10 && false"
        }
    }

}

echo "last line, done!"

def onErrorMarkUnstable(desc, Closure body) {
    echo "${desc}"
    try {
        body.call()
    } catch (org.jenkinsci.plugins.workflow.steps.FlowInterruptedException e) {
        def allowInterruption = true;
        for (int i = 0; i < e.causes.size(); i++) {
            // white list ExceededTimeout
            if (e.causes[0] instanceof org.jenkinsci.plugins.workflow.steps.TimeoutStepExecution.ExceededTimeout) {
                echo "${desc}: An error occured (${e.causes[0]}) marking build as failed."
                currentBuild.result = "UNSTABLE"
                allowInterruption = false;
            }
        }
        if (allowInterruption) { throw e; }
    } 
    catch (hudson.AbortException e) {
        def m = e.message =~ /(?i)script returned exit code (\d+)/
        if (m) {
            def exitcode = m.group(1).toInteger()
            if (exitcode >= 128) {
                throw e;    //  killed because of abort, letting through
            }
        }
        echo "${desc}: An error occured (${e}) marking build as failed."
        currentBuild.result = "UNSTABLE"
    } 
}