Reading through the docs for AEM as a Cloud Service for Dispatcher. Obviously there are a lot of limitations imposed there (still working through the "this won't be possible anymore" effects of it. One thing that struck me was this:
It seems that the Cloud's Dispatcher doesn't include BASIC! things like support for Server Side Includes... Are there any plans in place to improve this? The docs vaguely mention that in future it could potentially include more modules.... What's the reasoning for not having something as basic as SSI (paired with for example SDI)
I am no expert on AEMaaCS but what I think is the reason for not including everything to AEMaaCS because AEMaaCS is just not a migration to the cloud it is more. e.g. using microservices to do offline processing for assets, changing replication, etc.
There is a lot of feature from traditional AEM has been removed e.g. Campaign, Product etc. and getting added gardually.
But you can expore https://sling.apache.org/documentation/bundles/dynamic-includes.html to implement SSI in AEMaaCS if it is not available OOTB.