While a C++ compiler may not be allowed in the app store, one could add the code analysis part of clang/llvm for code completion and remote xcode control for compilation. 

It seems that this has not been suggested yet.
If a file is "open" in edit mode, it can be downloaded from web dav or even within the same app.

1) create a close button to allow people close the file, so to commit any pending change or whatever is necessary.
To "unlock" the file it looks like the only thing to do is to move to a different file. But it is going to create a loop if you don't have a dummy file in the folder.

2) within the file transfer panel, if someone attempts to delete an opened file, just propose a pop-up that inform the file is opened in editing. Ask what to do
a) close with save
b) close without save

I'm finding the small line, column view in the top right corner of the screen to cover the text I'm working with, and I don't need it. Is there a way to hide it?

If all files in one folder are linked to the same folder on the ftp server, then creating a new file should autolink this connection.
Maybe you could implement a toogle in the new file window, that this connection will be established automatically.

Hey there, good job. One minor improvement based on the Textastic 4.0 could be implementing the code completion for keyboard users as well. Right now, there's no way of using the keyboard to navigate through the suggestions and accepting them with the return key. else nice work.

Be able to for every extenssion type, or language, to create own shortcuts like "

Hi Alexander - any chance of adding code completion for different languages. I use HADOOP at work and would like to be able to add PIG, HIVE, JAQL support. I can create the schema templates if there was a way to add them.

You could include discount (http://www.pell.portland.or.us/~orc/Code/discount/) and use it to render a Markdown preview. It lacks Markdown Extra features like footnotes, but covers all of standard Markdown syntax and can easily be merged with Objective-C.