DC offset removal might be possible to do with the SVF module, if you use the high-pass output and set the cutoff frequency low enough so it doesn’t affect frequencies above DC.
inverting can be done using the VCA module. The QVCA module is a simple quad multiplication module, which could be combined with the normal VCA module to do rectification, just an idea.
if you have 2 samples playing and want to crossfade between them I guess you could send the crossfade signal to a VCA first to invert it, then send it from there to the amp mod input of the sampler, while sending the original signal to the amp input of the other sampler.
for slew, search the forum for a possible solution. there is no S&H module yet but it’s a good suggestion and has been mentioned before.
I have no idea what a mid-side splitter / combiner is?