I am close to convincing a large client to change its corporate presentation template (at least for one event). Here is my strategy:

• Convincing people that a high-profile, external event merits a format that can deviate from everyday documents that are mainly used for internal audiences
• [But this is the most important one] Comparing the 2 template options not based on a blank slide, but on one of the most important slides of the entire event. Seeing a straight comparison of what is, and what could be for one of the most important messages of the company makes deciding easy. You pick the one that looks better.