That is not building an alternative though. You are only destroying the current system by shooting the execs and are merely hoping that things improve.
It could be argued that a sustained campaign of murders where the selection criteria was known to be "execs who exhibit this behaviour" would have effects beyond the murders themselves.
Less "hope" and more "a plan".
Not necessarily a good one, but a plan nonetheless.
Building an alternative would be some way of dealing with sewage without dumping it on the beach. The main problem with that are usually combined pipes for rain water and sewage. So when you have heavy rain the sewage plant can no longer deal with all the sewage, as a lot of it is just rain water. The alternative for that is something like a sponge city, where the rain water goes straight into the ground and is not blocked by asphalt or the like. Other then that lowering sewage going to the company using say compost toilets might work or maybe buying up the company and turn it into a cooperative.
That is a well thought out list of potential strategies.
And none of it matters to the companies dumping the sewage, unless it's going to be more profitable for them to adopt one of those strategies.
Alternatives to dumping raw sewage already exist, dumping it is more profitable, even with the added cost of buying the political influence to get laws changed.
I'm absolutely not saying we don't do all or some of these things, it does make a difference , but we need to acknowledge that it's fighting an uphill battle against an entrenched system with goals that are usually diametrically opposed to allowing this kind of thing to succeed.
And make decisions accordingly.