Should a ground lease give Landlord right to consent to an assignment by Tenant, which shall not be unreasonably withheld

It is not uncommon, in fact it probably happens more often than not, that the lease provides that it can't be assigned without the landlord's consent.  However, the fact that the clause is common does not mean that the tenant has to agree to it, nor does the landlord have to agree to unrestricted assignment.  This is a matter for negotiation, just like any other term.  If one side is adamant, the other will have to decide if the issue is so important to them that they'll let the potential deal go.