This thread was very helpful as I have aimed to understand how to have different layouts for different kinds of tiddlers, ones which superceded the amount of flexibility afforded by the ordering of tiddlers tagged as a view template, which include different positions for the text field itself in relation to other fields.
Eventually I found another thread that explains the new view template “cascade” feature:
It’s now quite easy to add your own template and rules to the waterfall, without editing the core, in a manner which I believe Joshua’s “hack” initially elucidated.