Vladimir Zlatanov wrote:
1) Including lots of templates might be a performance drain; I've already done some experiments that show that even with an opcache, more PHP files with small amounts of code is significantly slower to process than 1 PHP file with lots of code. Though I think this could be rectified with a PHPTemplateCompiled engine, where the compiler extracts all of the files necessary and puts them into a single template file. This would have an advantage of making design easier by separating the templates, but impacting the performance much less...but it does have the disadvantage of the compiling process being a disconnect between modifying and using. Still, I think there could be some value here.
+++ as long as it is an optional feature, in some hosting environments you don't have write access to fs
Indeed, that is exactly why I suggest creating it as a completely separate engine. Though as I think on it, the current setup doesn't support running the same theme with multiple engines, that I'm aware of. I'm not actually sure.