Hi Foxi,
Indeed, the new Ventis is even better in light winds, I have to say it does take a slightly different technique to pump, but once you get used to it, it does have incredible power to keep going thru lulls and especially good for staying up above your head for gybes and tacks, without dropping down - so all-round for less skilled riders, perfect, also for the passive planing up onto the foil as you say.
For more experienced riders, with good pumping technique, of course a smaller wing is always possible, or you use a slightly bigger foil etc. The new Slicks definitely have a LOT more power than the 2022/23 SLS and also more than the 2023 standard and D/LAB versions. So with a 6.5 and a DW board, I think this will be fine.
Just to quantify for other people reading, Walchensee is a fresh water lake, relatively high altitude with a thermical wind. It does however have some peaks and lows - so it is not a super light constant 10 knots, therefore it is possible to use a smaller wing and just get up and go in these gusts/keep going thru the lulls. There are other locations where there simply is no stronger gusts/other lakes in Bavaria/Florida etc, where you really just need the bigger size Ventis to get going, especially if your pumping technique is not refined.
I was out recently in Cape Town at Rietvlei, fresh water Lake, with a very, very light SE wind of constant 9-11knots - I checked the wind meter afterwards - I stayed up on the foil for 35minutes, because if I would have dropped down I would never have made it up again - 6.0 Unit/1100 Carve/4'9" Sky Style - I got one gust and took it from there. So anything is possible, but you do need that one gust! :-)
DW Air should be fine yes, and in summer we may have something more compact indeed...:-)