Since https://github.com/TD-Addon/TD_Lua_Addons/pull/22 and https://www.tamriel-rebuilt.org/asset/add-openmw-global-variable-make-lu... have been merged, there is nothing stopping me from introducing this Dialogue line.

In the comment below you'll find an ESP which modifies the Passwall dialogue for the Mages Guild finale -- a new line is added right below the line responsible for giving you the Passwall spell if you use MWSE. The only difference is that a new global variable is checked if it's nonzero. That global variable is set to a nonzero value only if you use OpenMW and you use the TData Lua Addon.

Spell itself needs edits, but https://www.tamriel-rebuilt.org/asset/passwall-spell-magic-school-change... is responsible for that.