I don't get the systemd hate in this specific case. Their timers are pretty much the best possible option you have to schedule jobs, hands down. No cron Daemon is ever going to get there due to the lack of deep integration with the rest of the init system.
I know it takes a while to get used to the ini file madness, but honestly, I can't detect so much boilerplate there: every single line in my units and timers makes sense.
If you're not familiar with that system yet, I can only encourage you to at least take a look at systemd timers. They are really cool! :)
Hope it doesn't read like I meant hate to systemd, please let me know where if you feel like I did! I guess some of the cons I listed count as subjective, but I doubt anyone would argue that adjusting a systemd job is easier than cron job :) Also I emphasised that I had non-tecnhical user in mind, who would definitely have hard time understanding what are 'timers', and why their job type has to be 'Simple'.
But I agree that forcing cron into doing what it wasn't meant for isn't probably going to go anywhere. That's why I suggested that using systemd as a backend is probably the most reasonable option after all, if only there was a friendlier tool to make the process as simple as with cron.
I think you should check out mcron, which is basically cron redone but in GNU guile (scheme) with more features. I think it fails some of your requirements (the syntax can be a bit more to wrap ones head around than standard cron), but it is powerful and seems promising.
I know it takes a while to get used to the ini file madness, but honestly, I can't detect so much boilerplate there: every single line in my units and timers makes sense.
If you're not familiar with that system yet, I can only encourage you to at least take a look at systemd timers. They are really cool! :)