If your goal is to train engineers, my recommendation, as an engineer, is to stay away from the "more interactive" (also known as "more entertaining") approach that uses video, audio, and hot-zone mouse-overs. Contrary to what has been advertised, video and audio are actually very passive forms of training. We have seen that if you include an audio in a course (as an adjunct to slides), the learner often abandons the visual portion (since they are receiving audio) and drift to check their e-mails or other tasks they need to do. The result of this is that their focus on the learning is reduced, and eventually lost. Only 10% of material is learned through audio. Keep this in mind.
Engineers have been trained to be able to learn from visual content (primarily math and physics with lots of equations). We (engineers) are accustomed to both quick learning (by looking up a formula) and in-depth learning (understanding how the formula was derived). A video can provide an example of the concept, but will generally not provide fundamental engineering concepts.
True interactivity involves changing behaviors based on the student's response. The simple form of this is to provide the learner with multiple expositions of the same material accessed through links on a page. These expositions could include a step-by-step table, a link to a journal article, a formula derivation, a practical example of the implications of the formula, a quiz, a tracked test. The more complex form of interactivity (which is much more expensive) is a true-to-life simulation, such as Flight Simulator. People should really question what is interactive about a hot-zone mouse-over. If you are training people how to move a mouse, this is a good simulation; however, if the purpose is to teach some other concept, it becomes "eye-candy" (and can be very distracting). Every graphic, audio, video, hot-zone, or other non-text element should be carefully scrutinized and justified. Does it convey new information? Does the student's action relate to the content, or is their action simply a display control?
My recommendations: A good "book" layout will be most effective at training engineers. An instructionally sound "book" approach is more than a series of linked slides with a table of contents on the sidebar. Each "page" of content should include links to sub-pages with different expositions of the same material, since each learner will gain differently from each presentation. The material should be easily accessible, meaning that at any time when the employee is doing their job, they can use the "course" as reference material to look up the procedure or formula. If the course is designed as a one-time, linear set of content, you lose this possibility. If you can put a search engine on your site, and the content is properly searchable, you will create a re-usable resource that the engineers will quickly adopt as part of their "library" of knowledge.