Elsewhere you see dry soil plants just above the water, perhaps the most extreme demarcation I have observed is in the Potholes Reservoir, where there is barren aridity inches from blue water - maybe like in the Middle East etc.

I'd just be sure to allow for high water episodes and leave it at that, if they never get flooded by the ditch spilling over there should be no problem with the proximity of water.

You were missed at Florabundance.

The plants you mention specifically tend to be susceptible to root rotting pathogens when irrigated during the growing season. They have adapted themselves to soils that are dry when warm and cool when damp, conditions that are not favorable to soil fungi. They avoid infection by living in soils that don't support high populations of pathogens. When planted in soils that do support high populations of pathogens, then these plants are in trouble as they don't seem to have other methods of resisting infection.

I don't know about other dryland plants. I suspect it varies by species and by ecoregion of origin, but maybe not. I know that rare plant conservation efforts in Australia are complicated by the introduction of Phytophthora cinnamomi, and that native plants growing in well drained soils are less subject to infection than those growing in soils that are subject to waterlogging during periods of heavy rain. These plants can be wiped out by the pathogen, causing local extinctions and changes in distribution and abundance. So it could be that many dryland plants are susceptible to root rot when irrigated during their normal dry season.

Those are my thoughts on the subject. It would be very interesting to see how your plants do over the years.