Gerry Leonidas's page says tonos needs to be suppressed in all-cap setting.http://leonidas.org/greek-type-design/case-conversion-for-monotonic-greek/
While this itself is not new to me, I haven't actually supported this as an OpenType feature nor have I seen other typeface that supports it. If one needs to, there should be a code in "case" feature and "calt", where you check whether tonos-cap letters precede or follow another capital letter and substitute with tones-less alternates.
Is it necessary to include tones-less alternates, or support at OT level at all? If not, what is the reason?