If I understand correctly, you want ⌥⌫ to act as regular ⌫ when at the beginning of a line.
What you can do is overload ⌥⌫ for the case where you are at the beginning of a line (assuming you are using TextMate 2).
- Edit → Macros → Start Recording (⌥⌘M)
- Press delete (⌫)
- Edit → Macros → Stop Recording (⌥⌘M)
- Edit → Macros → Save Macro… (⌃⌘M)
- Select a bundle for where to save your macro
- Set key equivalent to option-delete (⌥⌫)
- Set the scope selector to:
L:dyn.caret.begin
- Press ⌘S to save the macro
Now pressing ⌥⌫ at the beginning of a line will act as if you pressed ⌫.