I always liked haggis and when I decided, about thirty years ago, to stop eating meat, haggis was the last meat dish I ate.
At that time it was impossible, at least where I lived, to find ready made veggie haggis and so I made my own, using crushed roasted nuts, bulgar wheat, oats, soya sauce, spices and lots of onion.
Nowadays it is easy to find readymade vegan haggis in UK supermarkets.
Although I know that whisky cream sauce is traditional for Burns Night, I prefer a rich onion gravy. I only serve tatties and neeps, never any other veg on Burns Night but there is no reason not to experiment with other veg as many combinations work well with haggis or vegan haggis.