I have fed veterans on soaked grassnuts and linseed with soaked unmolassed beet as necessary, with great success. We have just varied the amounts according to the individual horse's needs.
Why feed a specific veteran feed most of them are high starch and sugar which is the worst thing ever, if the horse is a good weight what are you trying to achieve with the feed?
If the horse is a good doer, I assume the only reason you're feeding is to get supplements or medication into them? In that case, ditch the veteran feeds altogether and go for something that has the lowest sugar and starch values possible. A low calorie balancer or chaff might work, but if they're not appetising enough, I'd probably try a small amount of Fast Fibre.
As JJS said, if you are feeding for supplements / medication or to give them something when everything else gets fed then anything low sugar and starch. I use fast fibre.