This happened faster than expected: Panasonic announces today that in the very near future (from mid-July) also the LUMIX S1 and S5 will be extended by an external Blackmagic RAW recording with the monitor recorder Video Assist 12G HDR. 
Only recently the S1H already supports this feature.
As with the first model, the S1 and S5 will offer true 1:1 5.9K RAW output (5888 x 3312, 16:9) at 24-30p and 12-bit colour resolution via HDMI.
In APS-C/S35, even C4K resolutions (4128x2176, 17:9) can be output at 24-60p, also in 12-bit.
And for anamorphic projects, there is also 3.5K recording with 3536 x 2656 pixels. Also in 12 bit with 24-60p.
Since the S1, S1H and S5 use a very similar sensor, the results of our tests of the S1H with the Blackmagic Video Assist 12G HDR should be largely transferable.
The most relevant difference for Blackmagic RAW recording is thus the much lower body prices of the S1 and the S5.
The required firmware update (V2.1 for the S1, V2.3 for the S5) should be available from 13 July on the firmware support website.
The S1 also requires an installed Software Key Upgrade DMW-SFU2 for RAW support. The S5, on the other hand, can use the firmware update without obligatory software keys.
With the new firmware, two new image profiles (L.ClassicNeo, L.Monochrome S) are also implemented for the S1, S1R and S5.
On the Internet, you can get an S5 and the 12G HDR Recoder together for well under 3,000 euros, which is a new price segment for a 6K RAW FullFrame camera (with 4K 60p option). Especially as Blackmagic RAW can then be edited very comfortably with the free version of DaVinci Resolve.
;)