Just as an observation, the adjective καινης needs to be put in there someplace. But laying aside all the fancy mode of address, one's choices are limited. the verb "to be" is in the present active indicative third person singular. The "is" means time is involved, and "present tense" means that the sense is that of an action in progress, something continually being. It has no other sense.
Thus, keeping faithfully to a literal interpretation, the language is simply either literal, or it is figurative-literal. There are no other choices. Literally, Jesus is saying that either (a) the bread loaf is of the same substance, character, and use as the flesh of His body, or that (b) its nature, preparation, and use are to be taken figuratively to represent the literality of His Body as a sacrifice. Jesus is also saying (verb tense) that the item of bread in His hand may be habitually regarded spiritually in its ritual ingestion as a reminder of His Body given for them/us. With these choices in mind, no sane onlooker could or would understand that (a) above is true, as being a literally transmitted fact.
Therefore, only (b) can be a rationally acceptable statement that the bread loaf in its current state can be viewed figuratively as illustrative of His Body (not his flesh) as a burnt offering. Note that he is communicating the abstract concept "Compare this bread loaf to my Body in a spiritual sense, not a literal, carnal sense."
The same hermeneutic process applies in the same way, to His announcement of the paradigm of ritually partaking of unfermented juice of the grape being (Gk present tense) a reminder of His Blood, that was to be shed for them as a sin offering.
No other interpretation is possible without introducing doctrinal schism in its explanation or application. The normal interpretation of this passage is a plainly obvious one attributing Jesus as using figurative expression, as He did at the time reported in John 6:35 and onward in that lesson, and which from Him the twelve learned of spiritual application of a literal object or process. Other disciples, interpreted what he said as speaking literally/carnally and not figuratively/spiritually, and walked away, not to return again (see Jm. 6:61-66 and be advised, especially 6:65).
Problems arise when something is read into a passage (eisegesis) that is not there, when a literal hermeneutic (exegesis) is abandoned for an allegorical one. The abnormal transubstantiation implementation is just such a one.
We say, "How ARE you?" but Spanish asks "Como estas?" where estas is a 'stand' (or "state" verb. And unless we have to, that's why I don't want to go running into that maze.
What you are introducing here in Koine would be the perfect tense, an action completed in the past with a continuing effect or consequence. This has no relevance to the verb tense you are discussing, if I may point out.
my Greek txt (Mark) didn’t have kaine. but I didn’t check the apparatus. I’ll look more carefully when I get home — if the thread hasn’t died. I did wonder....