An important bit of information I omitted: most of the footage in the sequences isn’t 30i native at all. Almost half is 720p/60, and a third is telecined 24p.
I expect to end with a 60fps sequence where for starters, the sequence in & out points will correlate. An in point at 1:00:30:23 would become 1:00:30:46. Leave H:M:S alone, double the frames. Pretty simple.
The footage should also maintain its ins & outs and be interpolated the same way FCP would treat it if I manually edit a non-60 shot into a 60 sequence. Needless to say native 60p footage should fit in a 60p sequence.
I see what you’re saying about 30i looking like crap in 60p – haven’t had a chance to test it myself in depth yet, but given FCP’s poor track record in pulldown (the “2:2:2:4” pulldown), I can see it screwing it up. Ideally FCP would deinterlace on the fly or with a plugin (map every field to a frame – simple 2:2 pulldown), without requiring a deinterlacing software.
I’m aware that getting everything right will require much tweaking, I’m trying to avoid having to overcut everything from scratch.
P.S. As for FieldKit alternatives, Compressor and Episode Pro should also be able to add or remove interlacing properly. TMTS has a Smart Deinterlacer plug-in for FCP, and on the PC side, AviSynth has some very powerful features for fields handling and deinterlacing.