I wrote a minimal patch that increases the overall consistency in a
backtrace buffer by printing the call stack frames as S-Expressions.

Before:

Debugger entered--Lisp error: (wrong-type-argument number-or-marker-p t)
  +(1 t)
  eval((+ 1 t) nil)
  eval-expression((+ 1 t) nil)
  call-interactively(eval-expression nil nil)
  command-execute(eval-expression)

After:

Debugger entered--Lisp error: (wrong-type-argument number-or-marker-p t)
  (debug error (wrong-type-argument number-or-marker-p t))
  (+ 1 t)
  (eval (+ 1 t) nil)
  (eval-expression (+ 1 t) nil)
  (funcall-interactively eval-expression (+ 1 t) nil)
  (call-interactively eval-expression nil nil)
  (command-execute eval-expression)

Now, this patch isn't perfect.  For some reason there's an extra debug
line in the second version, I've yet to investigate into the reason for
this.  The other problem is that while I can't imagine any reason to go
back to the original view of the backtrace, I cannot rule out that this
change might break other tools relying on it.  I'd appreciate any
feedback on this.