Hi Ivar,
First let me say congratulations on your expansion and new premises.
To the point of your questions, I do have some experience with the problem, albeit that I do not fall into the category of bicigrino you are talking about, since my problem has always been getting my bike back to Australia. But I do have some observations to make. Some obvious.
1. Bicigrinos fall into two categories: those who rent, and those who bring their own bike.
2. Those who bring their own, do so because they prefer the machine they already ride, and because, like me, the machine is more suitable and, as in my case, much more expensive than one they might rent.
3. The category 2 bicigrino has already solved the problem of getting their machine to the camino in the first place, and therefore is experienced in the process of packing and in the vast majority of cases, travelling with their bike to the starting point.
4. Having just returned from the camino (successfully with bike) myself, I could not help but notice the number of other bicigrinos flying out of Santiago with their bike packed in a designated case or bag (like me), or packed in a box sourced from either Correos, or a bike shop in the city.
5. I believe that the vast majority of pigrims in category 2 will prefer to fly home with their bike, rather than having it shipped by third party.
For these reasons, I believe there may be a very limited demand for the service you propose. I'll be interest to read what others may have to say on this.