No, the idea is that the same researcher should produce k papers and n replications, instead of just k + n published papers.

I'd argue that since replication is somehow faster than original research, the requirement would count a replication somewhat lower than an original paper (say, at 0.75).

That is my idea... If we opened it up, there's probably more interesting iterations, such as requiring pre-registration for all papers, having papers with pre-registration count as some portion of a full paper even if they fail so long as the pre-registration passed scrutiny, having non-replicated papers count as some portion of a fully replicated paper, and having replication as a separate category such that there is a minimum k, a minimum n, and a minimum k+n.

The non-easy part of this is once we start making changes to the criteria for tenure, this opens up people trying to stuff all the solutions for all of the problems that everyone knows already. (See Above.) Would some one try to stuff code-available for CS conference papers, for example? What does it mean for a poster session? At what point are papers released for pre-print? What does it mean for the tenure clock or the Ph.D clock? Does it mean that pre-tenure can't depend on studies that take time to replicate? What do we do with longitudinal studies?

I think you're looking at a 50 year transition where you would have to start simple and iterate.

Is tenure really as mechanical as "publish this many papers and you get it"? My impression was that it took into account things like impact factor and was much more subjective. If that were the case, then wouldn't you run into problems with whoever decides tenure paying lip service to counting replication or failed pre-registered papers but in practice being biased in favor of original research?

It depends on where you are. The more prestigious the university, the more that impact factors start to matter. There is also the matter of teaching and service, but I'm not talking about the entire tenure system.