For the purpose of our evaluation, we have been backing up to a NAS drive, but I'd like to retire that.
Be aware that VB&R provides disk-to-disk-to-tape scenario. In other words, it doesn’t backup directly to tape medias, instead, it archives already existed restore points. So, there still should be a place to where backup data goes first.
Reverse incrementals and weekly (Saturday) active fulls – this is to facilitate tape cutting for offsite storage
I’m not sure whether I follow you on that. If you’re using reversed incremental mode, each time tape job runs, it will copy a completely full backup. Also, in case of reversed incremental, the demand for performing active full also isn’t that strong – you should be ok with running active full once a month or two.
As to the possible architectures, scenario#2 seems to be preferable, since it’s not recommended to run backup software and DC on the same machine (as in the scenario#1).