The main problem with this solution is the auto-allocated private IP addresses. A restart (sometimes) or a full stop and then start (most of the times), might cause a change of IP. One trick to always get the same IP addresses allocated for the private containers is to limit the size of the subnet to the reserved addresses count (5 addresses)+ the number of containers (minimum allowed size is 8 in total).
Feedback has already been given on this issue, and can be tracked here: https://feedback.azure.com/forums/602224-azure-container-instances/suggestions/41222680-aci-with-static-private-addresses