Of the two translations you offer, the one we need to take most seriously is that of the eminent 17th-century scholar Denis Pétau ("Διονύσιος ὁ Πετάβιος"), who was fluent in both ancient languages. He saw that there might be a problem in making Greek ἔχειν equivalent in this context to Latin habere, so used a word more definitely related to possession-by-acquisition, i.e. κτήσασθαι.
As to his choice of ἐκφέρω ("put forward, disclose, bring up"), I find it too strong for Cicero's simple loqui. Your διαλέγεσθαι seems to hit the mark perfectly. (I have the same problem with Antoniadis' ἀνακοινοῦσθαι, "impart".) On the other hand, both Pétau and Antoniadis do try to reproduce Cicero's subjunctive in audeas with the Greek optative + ἂν after the indefinite τινα/ὅτῳ. Antoniadis accomplishes this with ἂν … τολμήσαις.
Finally, I see no difference in meaning between Latin audeo and Greek τολμἀω, so find it unnecessary to soften "dare to speak" as does Pétau.
Antoniadis' real contribution may be in using ἥδιον instead of γλύκιον/ γλυκύτερον. This has a genuine Platonic/Theocritean ring to it.