Once that's available, people will demand and abuse it, and we're back at cgi-bin.
Not in ngx_http_ssi_module or any modern webserver I've used? As for "people"? What people? I guess your implicit assumption is this is a group or commercial project? I was thinking more website made by a human person.
(I've still never seen the need to switch to more trendy web servers, so they may well have disabled exec)
Once that's available, people will demand and abuse it, and we're back at cgi-bin.