I love TextPad and the only thing that is keeping me from buying a license is the very slow development. Anyways, here are some things that I would like to see in the next version - most of them are already in TextMate for Mac OS X:
Comment multiple lines of code at once and differentiate between various languages (maybe addition to the syntax highlighting?)
Support for code snippets
This one is hard to describe - I would like to be able to type in "HelloWorld", press a custom key combination and the program automatically changes "HelloWorld" to something like "function HelloWorld(arg1) { }", selects "arg1" and moves the cursor to it so I can start editing the arguments. After that, pressing CTRL+TAB maybe or something and jump between "{ }" so I can type in the code for the function. Or instead of letting the user associate multiple key combinations for various actions, you could let the user type something like "_fnct_HelloWorld" and then press a key combination that is defined by TextPad and TextPad changes "_fnct_HelloWorld" to "function HelloWorld(arg1) { }"; type in "_msgbox_HelloWorld", press the key combination and TextPad changes to "MessageBox 'Hello World'". I hope you understand what I mean.
For your first wish: it should not be too hard to write macros for that (just replace the line start ^ with the single line characters for the specific language - // or # should cover quite a lot of languages)
regarding code snippets: did you test the Textpad Clip Libraries?
In part they could also be a help for your third wish.