@tomekslesicki yes, if you keep the value range the same, you should be able to switch to comboboxes for named plugin parameters without backwards compatibility issues. The plugin APIs do not store the text value in the DAW project, but the index and the text is a simple text lookup requested by the plugin API.
You might want to test this though as I can't guarantee that there are no glitches with this. Also watch out for off-by-one issues - zero in a combobox usually means not a value so the first item starts with 1.