Catch all pokemon with PKHeX

[Bzdoon]

What would be the best course of action if I wanted to catch all pokemon across all games? On the FAQ page it says you can't transfer backwards but there are also many remakes and so on. What order of games would I need to play to transfer all pokemon from oldest to the next oldest gens without being hit with technical limitations? I've heard you can't export from blue/red since they are too old. I haven't played pokemon for ages so I'm not really up to date with the franchise but I thought it would be a fun project to play through all of them and collect all pokemon. And this tool seems like a good solution to transfer them from one game to another but I would love some more input.

[Kaphotics]