In the Mishna on Daf 86A: Rabbi Eliezer says:even though it is not attested by witnesses at all, as long as he gave it to her in the presence of witnesses it is valid, etc.
In my Mishnayoth it says "R"A" - which is indeterminate. In other Mishnayoth it says Rabbi Eliezer. On the other hand: in the Yerushalmi Mishnayoth the reading is 'Rabbi Eliezer', as in the text of the Yerushalmi; and in the RIF; and thus says Tosfoth Yom Tov. However - could it be that there is indeed PART of the saying of Rabbi Elazar which are the words of Rabbi Eliezer - which would validate both readings?
Could it be that the saying of Rabbi Eliezer was: "even though it is not attested by witnesses at all" - since the requirement of wittnesses seems to be of Rabbinic origin, a Gezera for reasons discusses in the beginning of this tractate; and it would befit the general attitude of Rabbi Eliezer that rabbinical rulings are not as strict as are D'Oraitas, e.g. Shviit ch 8, mishna 9 and mishna 10 ? To this Halacha Rabbi Elazar concurrs, and adds his elaboration: "as long as he gave it to her in the presence of witnesses it is valid, etc". - since Rabbi Elazar is talking contemporary Halacha, and in his time - as we see Rabbi Maier - the Rabbis were stricter in the enforcememnt of the regulations of the wiriting of a Get?
If I am understanding you correctly, you wish to suggest a possibility that mid'Oraisa a Get does not need Edim. All I can reply to this is that Davar Davar mi'Mamon is a universally accepted Gezeirah Shavah and to paraphrase the Pasuk, Shelo Al Pi Shenayim Eidim Lo Yakum DAVAR.
Numerous times the Tana Rebbi Eliezer is quoted in the Yerushalmi as Rebbi Lazar (Lamed-Ayin-Zayin-Resh).
I do not think that being Meikil on a d'Rabanan can be used to determine a Man d'Amar, for this is universal other than the few places where the Chachamim Asu Chizuk l'Divreihem.