Not quite cross model architecture, but it's not impossible to merge different fine tunes of a model into one.

I personally have a few scripts for a few strategies such as

• Average merge;
• Diff merge;
• Block merging. (link)

I haven't tested diff merging or block merges too much (me and a friend finished adapting SD's block merge to LMs last week) but weighted average merges are a pretty safe way of mixing models.