In order to achieve effective alignment, a cross-funtional team needs to establish acceptable guardrails or ranges for the items that are likely to become part of a deal. Many teams go as far as establishing financial hurdle rates or other analytical tools to help quantify the value you trade when negotiating deals. Furthermore, although communication needs to be open and fluid, there also needs to be guidelines; "do's and don'ts" so to speak, so that the process remains manageable and true to the strategy you have outlined.
Secondly, 'expressing needs' during a negotiation is a useful part of the process and does not need to be viewed as a 'death-rattle.' Not only do we need to properly express needs and make sure that they are understood and well positioned, we also need to be able to 'discover needs,' by asking well-thoughtout questions and probing for underlying interests. Understanding each others' needs is what allows us to 'grow the pie' and arrive at more productive and mutually beneficial agreements.