[EricH]

As I see it, the question is simple: Can a reasonably complete robot go into the withholding allowance?

Let's discuss this from the rules.

First, what is the withholding allowance?

WITHHOLDING ALLOWANCE – A limited amount of FABRICATED ITEMS that are withheld from the ROBOT shipping requirements (specified in Section 4) and retained by the team following the shipping deadlines. These items are then hand-carried to a competition event by the team. The OPERATOR CONSOLE is automatically included in the WITHHOLDING ALLOWANCE. Beyond that, the incoming material maximums specified in Rule <R38> limits the amount of FABRICATED ITEMS included in the WITHHOLDING ALLOWANCE.

"Limited amount withheld from the robot" implies--note that it doesn't specifically say one way or the other--that you can't hold back your entire robot.

What is supposed to be shipped at the end of the build season?

<R26> [stuff that is general build season info]When the ROBOT shipment deadline arrives, all work on the ROBOT must cease and the ROBOT must be placed in a “hands-off” condition. The entire ROBOT (including all FABRICATED ITEMS intended for use during the competition in alternative configurations of the ROBOT) must be crated or bagged (as appropriate for your event), and out of team hands by the shipment deadline specified in Section 4 (with the exception of the items covered by the WITHHOLDING ALLOWANCE).

OK, so the entire robot must be crated or bagged, along with everything else, unless it's in the allowance.

<R27> During the period between ship date and the competitions: During this period, all teams may manufacture SPARE, REPLACEMENT, and UPGRADE PARTS, and develop software for their ROBOT at their home facility.
C. Teams may continue development of any items retained under the WITHHOLDING ALLOWANCE, continue to work on them during this period, and then bring them to the competition events.
D. The total weight of the FABRICATED ITEMS (SPARE, REPLACEMENT, and UPGRADE PARTS, plus all WITHHOLDING ALLOWANCE items) worked upon during this period and brought to the competition event(s) must not exceed the limits specified in Rule <R38>.

Next up, the rules on what you can do with the stuff in the allowance. Pretty much fair game.

<R38> Teams may bring a maximum of 40 pounds of custom FABRICATED ITEMS (SPARE PARTS, REPLACEMENT PARTS, and UPGRADE PARTS, plus all WITHHOLDING ALLOWANCE items) to each competition event to be used to repair and/or upgrade their ROBOT at the competition site. All other FABRICATED ITEMS to be used on the ROBOT during the competition shall arrive at the competition venue packed in the shipping crate or lockout bag with the ROBOT.
A. Exception: the OPERATOR CONSOLE is not included in the incoming parts weight restriction.

Aha! Here we have the definition of what exactly constitutes the allowance. Note that it includes 40 lbs of custom fabricated items from all categories.

Note that nowhere does any rule explicitely say, "Thou shalt not keep your entire robot as your withholding allowance." However, the rules certainly imply that you cannot keep your entire robot as withholding, even if it is under 40 lbs.

What I am going to say is this memorable quote from a Q&A back in 2008 in response to a very...err..."inventive" team: "That would be a violation of the spirit, but not necessarily the letter, of the rules." (Also note that someone figured out a way to bring a complete second robot to an event a few years back, and nobody's done it yet to my knowledge...)