General Ledger Instance Strategy and SaaS Limitations

We have a recent decision that requires validation and/or recommendation regarding ongoing deployments.

Context:
For all primary ledgers (one ledger per legal entity), the accounting key structure is common across all instances. It consists of 13 segments (including 3 reserved segments).
Our initial proposal was to maintain a single common key structure and create as many instances as there are activity/country pairs. However, the preference expressed is to have as many key instances as there are entities (with some possible groupings for certain entities).
Based on our analysis, this approach could eventually lead to around 60 instances combined with a unique structure.