A few more open issues, and use subheaders for each.

pep-0553.rst

@@ -82,10 +82,16 @@ returns whatever is returned from the underlying debugger entry point.
 Open issues
 ===========
 
+Confirmation from other debugger vendors
+----------------------------------------
+
 We want to get confirmation from at least one alternative debugger
 implementation (e.g. PyCharm) that the hooks provided in this PEP will
 be useful to them.
 
+Breakpoint bytecode
+-------------------
+
 Related, there has been an idea to add a bytecode that calls
 ``sys.breakpointhook()``.  Whether built-in ``breakpoint()`` emits
 this bytecode (or gets peephole optimized to the bytecode) is an open
@@ -95,12 +101,18 @@ bytecode streams to trampoline into their own debugger.  Having a
 in order to invoke this trampoline.  *NOTE*: It probably makes sense to split
 this idea into a separate PEP.
 
+Breakpoint arguments
+--------------------
+
 Does it make sense to define the built-in function's signature as
 ``breakpoint(*args, **kws)`` which would just be passed along to the
 ``sys.breakpointhook()``?  One argument for doing this is that it
 would allow users to pass useful arguments to their actual debugger.
 This isn't useful for ``pdb`` but might be useful for alternatives.
 
+Environment variable
+--------------------
+
 Should we add an environment variable so that ``sys.breakpointhook()`` can be
 set outside of the Python invocation?  E.g.::
 
@@ -110,6 +122,16 @@ This would provide execution environments such as IDEs which run Python code
 inside them, to set an internal breakpoint hook before any Python code
 executes.
 
+Call a fancier object by default
+--------------------------------
+
+Some folks want to be able to use other ``pdb`` interfaces such as
+``pdb.pm()``.  Although this is a less commonly used API, it could be
+supported by binding ``sys.breakpointhook`` to an object that implements
+``__call__()``.  Calling this object would call ``pdb.set_trace()``, but the
+object could expose other methods, such as ``pdb.pm()``, making invocation of
+it as handy as ``breakpoint.pm()``.
+
 
 Implementation
 ==============