I think you are simplifying Fe and Fi to action, correct? I.e., Fe users are automatically nice/non-offending, and Fi users operate according to their own values?
If this is how you are thinking of Fe/Fi, then you CANNOT develop Fe without abandoning Fi. On this last page, Marm says Fe IS a "personal value" (z) What this means is Fe's Fi (does this make sense?) is that "social harmony" is the most important thing. While Fi's Fi is whatever they have decided their Fi rules are (maybe they value social harmony above all like the Fe user, or maybe they don't give a shit about social harmony) Fi's Fi is totally individualistic, in that it can be anything, to determine what an Fi's Fi is you need to speak with that person.... whereas Fe seems to have "social harmony" as an ultimate value (through which everything else stems).
You wish you had Fe's social ease, but the problem is you have your own values where "social harmony" isn't at the absolute and never-changing top, so you are never going to behave Fe-like. Like you said, behaving Fe, I think, is just a rearrangement of your priorities... but because your priorities are different (your Fi's Fi vs. Fe's social harmony rule), you aren't ever going to become Fe without totally abandoning your Fi.
For clarity purposes/not answering the OP's question: Marm also said somewhere earlier in this thread that Fi's Fi (personal values) can be values that are shared by Fe's Fi. (And vice versa of course, but not the point.) I agree with this.