Not sure it is clever or sensible really. It seems both sides of the,argument regard the existing deal as unacceptable at present, therefore it's a fair assumption that there needs to be a renegotiation. The threat of no deal and the 39 billion are possibly the only leverage that can be used to draw the EU back into negotiations. Without that they will of course refuse to renegotiate what is an excellent deal for the EU as it stands. I'm not a great proponent of a no deal brexit, and actually very much doubt Boris is, as he's probably just playing to the gallery in the tory leadership elections. To legislatively remove no deal/perogation at this stage is manifestly stupid, although I could see the sense in it if it genuinely looked like Boris was going to do it. As it stands this just increases the likelihood of a deal very like the existing one being pushed through, which as we know seems to uniquely combine the very worst aspects of remain and brexit.