in your complex network scenario the need to use multiple EIGRP AS numbers may come if primary links are MPLS L3 VPN links using BGP as PE-CE protocol.
If so the risk is to see the desired backup routes, those via VPN/IPSec tunnels, to be considered the primary routes for the fact that using a single EIGRP AS domain would make those routes internal routes and could be preferred over the external routes derived from redistribution of BGP into EIGRP.
Under this hyphotesis, the use of a second EIGRP AS extending over VPN connections to make them the secondary routes.
I would not see the need for more then two EIGRP AS numbers unless you have two different backup networks.
note: if you are using EIGRP on primary backbone links you may want to consider the use of EIGRP tools and to use only one AS.
That is, playing with delay or offset-lists or also with ip eigrp summary-addess can be a way to deal with this.
Most specific routes are used first, so a way to make secondary paths to be backup is to advertise over them less specific routes.
This may be feasible or not depending on your address plan (if it allows for route summarization at remote site).
We are pleased to announce availability of Beta software for 16.6.3. 16.6.3 will be the second rebuild on the 16.6 release train targeted towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are looking for early feedback from custome...