fnork, i just read your original post one more time and a few more things jumped out.
you're proposing to play repertoire off the beaten path (unjustly neglected) and to research performance practice in the golden age of piano.
my advice is your proposal needs to show the relationship between those two things an easy one to suggest (an example only) is to look at cultural perspective in the music you play and the practice that you research. in other words, the lens through which you look could be focused to "read" cultural perspective and then your performance and your scholarship bring out that idea (for whatever you think it means).
but this example likely misses whatever really interests you (again, i'm just some voice out here on the internet ...
... anyway, the important thing is your proposal should have a grand arch so that what you play and what you research fall under that arch. by doing that, you make it really easy for YOU to see the big picture. and you make it clear to your committee that your artistic and research practice is linked and not two separate projects. in other words, one feeds the other and vice versa.
about the idea of "unjustly neglected:" .. that's a pretty common, ubiquitious catch-all phrase. but what does it actually mean? for example, why and how did mendelssohn champion bach's music? how did he do it? what are the artistic and critical paths he applied to show bach's music should be played and programmed and studied. or another example is gustav mahler. his symphonies came into the repertoire because leonard bernstein and a few others began to program them in mid 20th century. so how and why did that happen? how and why did it take that long to get someone like mahler into common practice! ? !
or there are composer who promote, for whatever reason, the music of other composers. gunther schuller's an example in the states. he's led so many festivals and what nots where he championed a million composers he thought were interesting and should be heard. now, gunther schuller doesn't now have the influence he once had. but there was a time (50s and 60s) when some of the "unjustly neglected" got quite a helping hand from him.
maybe a larger question in this is "what are the paradigms of bringing the unjustly neglected into common practice?" in other words, despite the fact that a million and two composers, performers, conductors, etc. have championed unknown work, there' are probably a limited number of common strategies and reasons that have driven what they've done and which have been used to bring new work to the public. or maybe instead of new work, the idea should be something like music composed in some previous time that begins to however it happens gets cache some years later in the future.
you might look at pierre boulez and IRCAM in Paris. there's an example of a composer who more or less went to the national government and said "fund contemporary music and research! do it now! and do it big!" he put his name behind it. so for example, Kaija Saariaho was an ircam beneficiary. (for all i know, she's your neighbor in helsinki ..
.... why did boulez promote her work? what did he get from it? what did the music world get from it? how did ircam benefit?
by looking at previous methods you can build on them or disregard them or subvert them or challenge them or disgard them, whatever. but the point is, there's a historical thread among the "unjustly neglected" and part of that thread perhaps is "unjustly neglected" is a modern invention in western culture where the concert hall exists as place to "verify" the worth of composers and performers. now, i'm not arguing at all that that's true. ...
one more take on it ... if the ligeti piano etudes sprang out of nowhere, say if ligeti really WASN"T known as the major composer that he is known as, etc. well, in that case, perhaps they'd be neglected because pianists would say they're unplayable. same for elliott carter string quartets. so conlon nancarrow's piano music (for player piano) might fall into this group.
... the disclaimer once more ... i'm not suggesting any of the above is true or what you should do. i'm just describing it as an examples of how to look at the "unjustly neglected" and to do more with it than dig up repertoire say "here's music that got overlooked!" maybe the "unjustly neglected" got neglected because the "golden age of piano" performers for whatever their reasons didn't want to go to wherever those unjustly neglected works went! in other words, maybe there was a "limit" to what golden age pianists performed and maybe whatever that "limit" is is the unifying idea behind the repertoire you play and the performance practice that you research.
hope this helps
... maybe one more thing to say is in the proposal writing stage, really, think big! and then think practical later! think big as in "what would you like to play and research do over the next bunch of years that'll keep you awake at night because it's so interesting and, the same, which will wake you up in the morning because it's so interesting!