I've researched the same concept myself for similar reasons - specifically to "merge" two independent cDot clusters together. It is simply not possible to do aggregate moves by physical shelf installation anymore.
The underlying reason is the metadata. An aggregate with the accompanying volumes in 7-mode are fully self described by the WAFL filesystem on the disks. In cDot, they are not. The cluster database, a copy of which is maintained on all nodes in the cluster, contains a ton of reference pointers as to what is where, what SVMs stuff belongs to, other relationship data, etc. There is no mechanism or utility that exists to map/merge 7-mode generic volumes into a cluster, building up the cDot metadata and ownership as you go.
I'm told by those with inside knowledge that cluster to cluster merge is something the DoT developers consider as a magic target if it could be automated mainstream, but 7-mode to cluster mode isn't even on the radar. With the existing data migration tools, and the fact that 7-mode is now officially EOL, physical aggregate migration between 7-mode and cDot isn't in the cards.