sometimes is not so much the stopping distance that is the most limiting actor in v1 calculations
Indeed.
For low levels of contaminant, ASD might be the worry due to reduced braking capabilities while TOD isn't affected all that much.
As the degree of contamination increases, the bow wave slush drag assists stopping but hinders going. Eventually a point is reached where the slipping problems for stopping are overcome by the drag benefits .. but the downside is that eventually the wheel drag overcomes the OEI thrust component and it all gets just a bit too difficult to contemplate.
My take ? If there's much in the way of stuff on the runway, time to consider coming back some time later and having a look again then ..
And the whole lot is further complicated by the variability of the specific slush ... talk about commercial interests competing with rational engineering and pilot command decision making ..