There are cases when I want to add a block in a template using template logic, but it does nothing.

For instance, when I have the condition (below) in a block and insert the block in the index template there's no input. However, when I add the condition directly into the index template it works.

{{if in_array($category->id, array(1))}}
	my_content_here
{{endif}}

Sure I can add the same code in a custom template, but I'll have to create a custom template for every theme I use. I rather make a block into the templates so when I modify that block all of the templates get updated.

Or is it already possible using blocks?

Yeah, it's rather annoying the number of places you have to edit the same code on many, many pages.