How to obtain the Raman spectrum along every coordinate of a scan in Gaussian?
No, there is no automation for this, and there should not be.

Using compound jobs is unfortunately very common among computational chemists, but they should always be viewed critically. If you are using any kind of IOp, then the probability that the second part of your job is doing what you want is low. Additionally, you do not really have any control about what happens if something happens to fail. In such cases, you also give up control over the validity of your checkpoint-file, which you might want to reuse.
Another issue is that these are basically two jobs running one after another and in most cases need different memory requirements, are more effective with another setup. It's the dream of every administrator (and co-worker) when you block resources you don't need for an extended period of time just to avoid a little more waiting.
Lastly, with the introduction of %oldchk= in in revision D.01, it is completely superfluous. Every well organised queuing system should be able to run jobs one after the other when specified (i.e. let one job wait for another to finish).

Only run compound jobs if you are 100% sure they cannot fail (and even then it's questionable).

From a theoretical standpoint, you should consider how much sense your approach makes. As TAR86 pointed out, Raman intensities are expensive. Additionally frequency calculations are only meaningful at well converged local minima structures. You are employing the harmonic oscillator approximation, which will break down if you are not using a local minimum (or at least a stationary point).

If you really need this approach, then you need to do it manually by extracting the geometries (and possibly the MO) and perform the frequency job on top of it.