Why can't we merge multiple templates and Repls?

I really wouldn’t want to have to use multiple Repls using multiple Templates, is it possible to merge them or will it be possible soon?

If I understand correctly, you are wanting to combine the aspects of multiple templates into one template. This would likely be difficult, as templates have different packages installed, different configurations, different things happening when run, and some operate on older Repl structures whereas some are newer. I suppose the creation of such a feature would be possible, but I doubt it’s likely. I could be wrong though.