I do not see that 1-2 being available, nor do I see him becoming available in the next month.
The problem with hankering after a TOTR starter is that literally all 30 teams hanker after a TOTR starter. That means that that guy is just often not out there and when he is, everyone else wants to give an arm and a leg for them. To suspend your search for all possible upgrades for the rotation while you wait for a trade that may never happen and might not even be a good idea if it does, is foolishness.
I agree with you this much -- Yordano ventura is not someone you acquire with your mind on getting a top of the rotation starter. My position is that Ventura fills our immediate needs and far more importantly than that, is the bird in the hand, a guy you can get, now, that fills a need now. In that light, holding out for rainbow moondream tradess will not win this team any games between now and July 31st (which I see as the first realistic time one of those TOTR guys might become available). Having Ventura in the rotation might win you 1 or 2 more games in this tight division so it should be pursued.
Make the trades you have to make, now, to improve the team, now, and get us maybe another game or 2 in the standings over waiting for the deadline and maybe having to sit pat because someone else blew your trade proposal out of the water for the guy you wanted. This choice does not seem particularly hard to me.