Sure, we already have the KISS approach: define indexBase in the default index and nothing else. Things are nicely put in a subdirectory or set of subdirectories. I don't think 4 (or so) properties are more KISS than one with templates.
Since the introduction of {{IndexManager}} s the term index name has a dual meaning. Initially it was used to specify the actual directory name of a filesystem based index ({{FSDirectoryProvider}}). Now the term index name is used to identify a {{IndexManager}} for example within the {{IndexManagerHolder}}.
This leads to ambiguities. For example:
{...
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