For discussion’s sake – while I don’t know the specific nature of your videos, my guess is that they might be demonstrating various techniques or other content in which simply hearing the audio of the video wouldn’t deliver the full context of the content. If making that content accessible is something you’d want to do, you’d likely want to start with a written description of what takes place in the video. Beyond that, high contrast vector images or diagrams showcasing specific parts of the technique would certainly help.
Predictable: Websites should operate in ways that are familiar and predictable. When a new page element is in focus, the website should not initiate a change of context such as opening a new window or going to a new page. In addition, the website should warn of user-initiated changes of context ahead of time, for instance through the use of a submit button. Navigation and labeling should remain consistent between different pages.
The type of operating system and hosting doesn’t matter much for design, but the platform is a factor. For instance, if you need a WordPress theme, the designer must work with WordPress themes and customize them in a way that a developer can feasibly code in CSS or JavaScript on the front end. If you use another CMS, the developer must work with those elements. Most designers specialize in specific platforms, so review their portfolios and experience for specific platforms before you invite them to bid on your project.
Most recently, however, pizza chain Domino's has been brought under suit for their website not being accessible for specialty ordering. The U.S. Supreme Court refused to review the case, instead upholding the decision of the 9th U.S. Circuit Court of Appeals who said the “alleged inaccessibility of Domino’s website and app impedes access to the goods and services of its physical pizza franchises—which are places of public accommodation.”