Should products not speak for themselves?
My understanding of your work environment is this: you have a lot of Microsoft trained professionals in a location where a lot of Microsoft products are being used. You’re going to be advocating to swap to alternative software (in the case of #2 and #3); maybe send everyone off to courses or replace everyone with employees who are trained in an entirely different ecosystem?
The Microsoft option is expensive, the training option is expensive, and the third option is ludicrously expensive.
Going back to products speaking for themselves: if you’ve got great products like Microsoft Excel, Vim, H&M standard hairbrush, then you can show them to people, and people use them if they’re suited for the need of the person or legal person.
As such, #1 sounds great, albeit empty. It’s not a strategy, a plan, or… anything that does anything, does it?
#2 sure, if you can afford to! It sounds good, and it works well enough where I work (I can open the .odf files of a colleague just fine) but I don’t see how this will do anything? It sounds like it would be something that would come across as “you cannot use this pencil anymore, you must use this other specific pencil with the same color that’s in the drawer” to all the other employees.
#3 I don’t know about your situation, but if there was a reason to not do so before, then why do so now?
So you’re perhaps looking for problems where you can propose a solution that is free software. It might be more effective to show where it could be better, instead of being an alternative for ideological reasons. An example might be your #3, if it is a cost saver in more than the licensing costs.
As for convincing IT guys, I would also not like to be chastised for not having all my clothes being bio cotton by a organic enthusiast. But if that person shows me the benefits of wearing bio cotton socks to work, then I would surely be more and more interested, instead of a company policy that says I should prefer bio cotton socks when possible.
Sorry if it is unclear, feel free to ask for clarification, and I hope you post your results and what the people you will present this to, will think about it.