You're not likely to make this work just by doing template edits. What you are seeking is going to require hacking the showthread.php file so that it calls the same functions and templates used to generate the "smiliebox" (hint - search for that in your PHP files to get a start on it) and parse the mouse clicks for clickable smilies.
I'm afraid it is going to add quite a few queries to your showthread.php file also which may incur a significant hit on performance for your users.
Personally, I just provided a link to the smilies listing in the quick reply box. It doesn't give my users clickable smilies but it does show them the legend for the smilies available. Zero queries added to the generation of the thread view that way.