I think the bigger question is the overall utility of this mod, which depends on the use intended.
If the intent is to "stealth" or record performances with the recorder concealed (say, in a shirt pocket), it is worth pointing out that the quality of the recording will likely be significantly worse than a comparable recording made with the same mics mounted higher up and aimed more properly (I'm not intimately familiar with the R-09's mics since I wouldn't use them for anything other than interviews, but I believe they point out from the "top" of the unit, no?). People can debate for hours whether mounting mics on your chest or collar is as good as mounting on your head. I suppose my answer would be, sure, if you're 7' tall. And actually, even then, I'd still want the mics on my head....
If you're going to put the thing on a stand or some other type of boom, then it seems like a wise one-box option. Given that the price is, I believe, also comparable, I'd think CA-11>battery box>R-09 is a smarter move than changing out the mics. Just my $0.02