Having read and re-read the OP, I'll go ahead and throw in my two cents.
Neutral on the Training changes. They could be good, but I'm super weary of making stuff take longer. Getting ARC trainings already are a huge pain, so unless you are seriously going to ramp up how many are hosted this may just make it much harder to get things moving. Also, I'm curious: If people have passed selections, but for some reason or another haven't completed the other two, do they have to re-do selections under the new system you are thinking of implementing?
+1 on the ARCT. I like the idea and I'm in favor of letting people "play around" with their new toys, yes there is potential for abuse but as long as its monitored this shouldn't be a big issue.
-1 on mandatory recerts. Unless you are going to significantly change the content of the trainings, there is no need. And if you ARE significantly changing the trainings, well, then this is a wipe in all but name. Note that I said mandatory recerts. If you instead allowed recert as a current Arc as an option rather than mandatory I think you'd get a lot less pushback, people that aren't interested in retaking it won't complain and those that want to be caught up to snuff will have the option and ability to do so.
Anderson