I too hope that Bourgeois's day will come. You mention Havergal Brian and Rued Langgaard. As far as Brian is concerned the rediscovery of his music began towards the end of his very long life and was inspired by the promotion of the music by his passionate advocate the composer Robert Simpson. Simpson was, at that time, a BBC Music Producer and used that position to get Brian's symphonies performed and broadcast. Since then the dedicated support and financial power of the Havergal Brian Society has enormously facilitated the recording of the music.
What is required to revive a neglected composer's music is a combination of factors. It helps if the music is broacast. In the UK that means that the BBC has to demonstrate an interest. BBC music producers have to be aware of the composer's existence and willing to push for broadcast performances. There have to be conductors willing to learn the music. This is less likely nowadays when there are fewer British conductors regularly conducting regional orchestras.
Record companies are also crucial. The reality again nowadays is that companies like to record a series of a composer's music. This is where the sheer number of Bourgeois's symphonies works to his disadvantage. Had he composed a dozen or so then he would have more appeal to a label which might show some interest.
It is, sadly, not necessarily a reflection on the quality of the music but is more to do with the interest/support of those who have the required influence. This is the difficulty Bourgeois faces.
Harsh reality......but never give up!
I agree with all you said. He is actually quite popular and well performed in the concert wind world and especially Asia (which came as a surprise to him). His first 7 symphonies were all broadcast by the BBC which was the point where he retired and moved to Mallorca and became explosively productive. You don't think it will be more like Weinberg (I forget how many symphonies he composed) but there are so many that no single record company records would record it but a few symphonies show up here and there in a variety of labels and in time we get all of them? Also working against him, some of these very prolific composers like Brian and Langgaard also wrote some quite short symphonies so it's not unusual to see four symphonies in a single release. With Bourgeois, they are long symphonies with very few short ones. Still, I hold out that a musicologist or someone will investigate the wealth of his oeuvre and put together a reasonable first orchestral project which could build up interest in conductors, broadcasters, public. I get that this is a bit of a chicken and egg problem. Till then, I will have hope.