Sounds like the aforementioned E-M5 is worth a look, as is the NEX6. Both would seem to meet on pretty much all needs. Sony NEX peaking is probably about the best out there, with adjustable strength and color to suit needs.
And just to confirm, there's no limit on Bulb mode on Sony NEX or Alpha cameras.
Sony DSLR-A580 / Sony 18-250mm / Minolta 50mm F1.7 / Sigma 30mm F1.4 / Tamron 10-24mm / Tamron 200-500mm / Tamron 90mm F2.8 macro / Minolta 300mm F4 APO
Sony NEX5N / 18-55mm F3.5-5.6 / 55-210mm F4-6.3 / Pentax K adapter / Konica K/AR adapter / bunches o' Konica & Pentax lenses!