One addendum to the above - it would be wise to clarify who is getting the BPS , I'd imagine it would stay with you in which case pepper corn rent is fine if he does the work to a high standard
If the BPS was transferring to him i'd want to get most of it back in rent in addition to the works etc.
Tenancy wise you can draw up a grazing agreement yourself , but if you go the FBT route i would definitely get a professional to look at it before you use it
(disclaimer I am not currently a smallholder, though i'm contemplating making the leap - However I am currently a team leader for the national trust and do a lot with farm tenants /tenancies as part of the job)