Question
When the grappler attempts to maintain the grapple (PH 156), how much movement can the grappler take to move into the target's space?
Comments say this issue apparently goes unaddressed in D&D 3.5's various discussions about grappling. (Seriously, I couldn't find anything either; that's why I asked.) If a by-the-book answer doesn't exist, here's an alternative.
If the rules are silent on this, what is a good house rule for movement the grappler can take to move into the target's space when the grappler attempts to maintain the grapple (PH 156)?
Background
Last night the thief ("A rogue is just a pretentious thief") was attacked by an advanced giant cockroach (Und 87-8), whose space is 10 ft. x 10 ft. and whose reach is 5 ft. Adjacent to the giant cockroach is an unfriendly advanced ripper (Ci 131-2). The map looked like this:
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----CC---- All 4 Cs = 1 giant cockroach
----CCR--- R is the unfriendly ripper
------T--- T is the thief
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The giant cockroach started a grapple versus the thief. She'd exhausted her attacks of opportunity. The giant cockroach succeeded with its touch attack to grab her. The giant cockroach won the opposed grapple check, inflicting its unarmed strike damage (which was a small die as the giant cockroach lacked monk levels but a large bonus as giant cockroaches have impressive Strength scores--who knew?). Then it was time for the giant cockroach to maintain the grapple.
Starting a Grapple under the heading Step 4: Maintain Grapple (PH 156) reads
To maintain the grapple for later rounds, you must move into the target’s space. (This movement is free and doesn’t count as part of your movement in the round.) Moving, as normal, provokes attacks of opportunity from threatening opponents, but not from your target.
If you can’t move into your target’s space, you can’t maintain the grapple and must immediately let go of the target. To grapple again, you must begin at Step 1.
The Special Movement Rules under the heading Accidentally Ending Movement in an Illegal Space (PH 148-9) reads
Sometimes a character ends its movement while moving through a space where it’s not allowed to stop. When that happens, put your miniature in the last legal position you occupied, or the closest legal position, if there’s a legal position that’s closer.
The Moving through a Square rules under the heading Ending Your Movement reads, "You can't end your movement in the same square as another creature unless its helpless" (PH 148)"
I know that the movement from Maintain a Grapple is an exception to the Ending Your Movement rule. That's not a thing. What is a thing is the giant cockroach's shortest route to maintain the grapple meant occupying the same square as the ripper, and that isn't legal.
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---------- Both Cs = 1 giant cockroach
-----CR--- R is the unfriendly ripper AND part of the giant cockroach
-----CT--- T is the thief AND part of the the giant cockroach
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Movement is movement, even if it's free, and while square occupation is largely waived for the grappler and the target, it isn't waived for any other creatures. At the table, I ruled that the giant cockroach was forced back to its last legal position, but I want to make sure. Could the cockroach have taken a different route--perhaps even all the way around the battlefield or even the world (perhaps provoking attacks of opportunity along the way)--to get in a position to maintain the grapple instead of taking the shortest route?