Spring AOP: How to invoke code before transactional method invocation, but after transaction begin?

Question

We need to perform some operations just before any transactional method invocation (insert*, update*, ...), BUT - it's important - after the transaction begin. We used to do it for years in that way:

    public class CustomBeginChangeAdvice implements MethodBeforeAdvice {
      @Override
      public void before(Method method, Object[] params, Object target) throws Throwable {
        (...)
      }
    }

    <bean id="beginChangeAdvice" 
      class="some.package.CustomBeginChangeAdvice" />

    <bean id="transactionProxyBase" abstract="true">
      <property name="postInterceptors">
        <list>
          <ref bean="beginChangeAdvice" />
        </list>
      </property>
    </bean>

    <bean id="transactionProxy"
          parent="transactionProxyBase"
          class="org.springframework.transaction.interceptor.TransactionProxyFactoryBean"
          abstract="true">
      <property name="transactionManager" ref="txManager" />
      <property name="transactionAttributes">
        <props>
          <prop key="insert*">PROPAGATION_REQUIRED</prop>
          <prop key="update*">PROPAGATION_REQUIRED</prop>
          <prop key="*">PROPAGATION_REQUIRED,readOnly</prop>
        </props>
      </property>
    </bean>

but now, for some reason, we had to rewrite our XML configuration (we don't use annotations, it's an old system) in that way:

    <tx:advice id="txAdvice" transaction-manager="integrationTxManager">
      <tx:attributes>
        <tx:method name="insert*" />
        <tx:method name="update*" />
        <tx:method name="*" read-only="true" />
      </tx:attributes>
    </tx:advice>

    <aop:config proxy-target-class="true">
      <aop:pointcut id="beans" expression="(
        bean(firstLogic) || bean(secondLogic) || ...
      )" />
      <aop:advisor advice-ref="txAdvice" pointcut-ref="beans" />
    </aop:config>

and now we face the problem: how to make our beginChangeAdvice work as before, but without creating a custom proxy?

We've spent last few days on it, but couldn't find any working solution in Internet. The worst, there is very few info on an XML-like configuration. Of course, most people use annotations today, but this is too much work for us to rewrite a whole system for now. It's pretty huge thing. Is there anybody who could help us? Thanks in advance, Peter.