This only works with Resolve, right? That makes it useless for on-set DIT use in which Pomfort's LiveGrade is used regularly.
At that bit rate 4k is pointless. Even Ultra HD (not DCI spec 4k) bluray discs have a slightly higher bit rate than that. And that's compressed for delivery.
A hard drive will only handle compressed forms of 4k which is fine for editing from proxies but not so great when you're at the latter stages of post and require pristine uncompressed versions of the footage.
When you start handling uncompressed forms (like a 10 bit 4k DPX sequences) then you'll need a storage array with a minimum data rate exceeding 1000 MB/s. For reference an average HDD generally does anywhere from 80 - 120MB/s.
That equipment will cost you.
That's fine for small productions but when you start scaling it up doing all your own stuff becomes difficult.
I work on small productions so there is no guarantee the production company will be able to access LTO tapes (or at least the version I use). But what I do is to have an SAS card (with external ports) in an enclosure. That way I can use LTO drives if the production has access to one.