HR Management System
I would like to suggest that Manager is going to be good if it can be made to have some HR features such as Employee benefits, hiring process , annual Vacation, leave salary, bonus, insurance and gratuity - End of service (HR related records) since it deals with income and costs of a business, and seeing that salaries are part of expenses.
I would suggest that these functions are best served by using a localised HR/Payroll system and then entering the total costs in Manager each pay period.
The highly specific needs for each country in terms of culture and payroll taxes are best met by local software providers or at least by large software providers with local branches
The tax rules and payroll and employment regulations are very different from one country to another whereas double entry accounting is more or less the same the world over bar local tax reporting
Have you tried adding these custom fields to the “Employee” file. See Use custom fields
If your customisation works well you could copy it to an otherwise default Business, then export it and share it. That way others may benefit for your brilliance 