Had a look at a meaty haggis recipe here (contains meat/offal, not for the squeamish). I'm thinking onions, (toasted) oatmeal, sage, thyme, rosemary, savory, (veg fat) suet, salt & pepper rubbed together and bound with a stock/lentil mix would be a good start, then steam it wrapped in foil (instead of setting out on a short notice and probably fruitless quest to find a vegan alternative to intestine) for a few hours. Perhaps a few more veg in there but not swede (rutabaga) or potatoes as they are traditional accompaniments.
Insights and suggestions welcome.
Edit: For the record, I avoid using meat replacement products (i.e. ground round or burger-style crumbles which I've never seen in the UK) as they can be price prohibitive for cooking at Kebele or don't taste that great compared to wonderful veg.