Don't depreciate yourself : so far the ideas proposed are quite limited and can be resumed to "OTL equivalent, but the brand change".
For others places like, by exemple, Sudan, Arabia, border expansion would have worked as it's more in the direction of Roman interests.
Now, even with an early POD (not too early in order to have a distinct "eastern" orthodox church from a "western" one you have to deal with both concurrence from Latin Christianism in northern Europe and Byzantine interests which were pretty much absent on north of Carpathians.
But, while direct influence from Romans seem implausible, using your idea for an earlier christianisation of OTL Russia, or maybe Khazaria could lead to an indirect orthodox evangelization.
The idea was proposed, but without too much details, so there's something to follow there by mixing both.
Hmm so Christian Churches that are in communion with both branches and use that to maintain autonomy (at least until the Latin Church has enough power to back its side)?