Your concerns make a ton of sense and I’ve been thinking about the same things for some time. I definitely agree we should be having more conversations about the effects of replicated security on centralization and validator sustainability. This is a big part of why the Duality proposal will suggest routing 100% of network value from the deployment back to the hub.
Longer term solutions are needed. Here are some of the ones that have come to mind in the past.
Facilitating replicated security chain M&A. While not every case will make sense for this, it feels likely that some might. This would void the fixed costs of adding additional consumer chains as no new chain needs to be spawned. That said there are high coordination costs for something like this as previously disconnected teams will need to become closely aligned in vision and roadmaps.
Rollup Centricity. Another thought would be for future versions of ICS to endorse rollup-centric architecture. In this world Replicated Security chains can act as settlement, sequencing or DA layers for rollups. With the introduction of Celestia into Cosmos, my guess is that it’d be best for the hub to align itself with Celestia through the former functionalities (Settlement and Sequencing). Nick White has talked at lengths about how to use the Hub for these as well and I agree that strong alignment is in the best interest of both. We’ve been working on some of these things at Duality Labs recently, would be happy to chat more about it on a call sometime.