Hello @Pinni3. To get to your points:
For that purpose, we allow nested dynamic groups. Meaning you have your 30 static ones, each one of them could have nested dynamic groups. Our you want to set it in a way, that you for example put the DG under "all" but then say that it needs to be only in the following static groups. Challenge is, that DG is evaluated on the Agent side, and Agent does not always know, in which SG it belongs to (if you move a client, it will need to recalculate all policy assignments for example). Therefore the nested concept.
We are already tracking improvement for that (Internal reference - IDEA-1100)
We are working on better auditing changes, to track who / what / when / how was done. (internal reference - IDEA-1371
I am not completely sure what´s the problem here. Purpose of ERA proxy was just to aggregate the data, but at the end it was sent to ERA server, so the amount of DATA sent is not increased when Proxy was deprecated. Just the ESMC server handles more connections directly, due to a changed replication protocol. Also, AFAIK we have bigger installations than 10k on MySQL. Maybe @MartinK can provide some more information on this.