There are couple of limitations with Profile Merge rules, so we need following updates in AAM:
1. Increase the limit on number of profile merge rules per account. Last month we raised this as feature request: JIRA ticket number is AAM-30258
Current Limiation: Since clients can have multiple different types of declared IDs, for example: Prospect ID and Customer ID. What if they want to later on set up Adobe Campaign Declared ID integration. Current limit of 3 Profile Merge rules cannot cater any extra declared ID data sources in future.
2. Increase the number of cross device data sources for profile link device graph . JIRA ticket number is AAM-34131
Current Limiation: We cannot choose multiple data sources while selecting the device option as Profile link device graph as it only allows to select one cross device data source, unlike Current Device where we can select upto 3 Data sources.