This is a subjective opinion, but I think a text editor shouldn't do everything and the kitchen sink. I prefer lightweight flexible and powerful (in their specialized fields) editors. Although being mostly a Windows user, I like the Unix philosophy of having lot of specialized tools that you can pipe together (like the UnxUtils) rather than a monster doing everything, but not necessarily as you would like it!
Find in files is on the border of these extra features, but useful when you can double-click on a found line to open the file at the right line. Note that initially, in SciTE it was just a Tools call to grep or equivalent!
FTP is very close to off topic, although it can be seen as an extended open/save dialog.
Replace in files is too much IMO: it is dangerous (you can mess lot of files at once) if you have no preview, etc. I would rather use a specialized tool I chose, perhaps among those in Multi line search and replace tool.
To answer the question, looking at N++, I see a Run menu where you can launch any tool, with assignment of a name and shortcut key. I see also Plugins > NppExec, which seems able to launch stuff like sed (not tried it).