Numenor is a good ally, both thematically and tactically, as they can provide you with numbers, whereas the Fiefdoms are more of an elite army than Numenor and provide different weapon options.
A front line of Elves with Heavy armour and Shields, backed up by a line of Warriors of Numenor with Spears and shields would work similarly to Dol Amroth Men at Arms, with the ability to shield if the enemy breaks past the Elves.
At 700 Points you could have Elladan and Elrohir leading some High Elves (1/3 Shields and Heavy armour, 1/3 Spears, Shields and Heavy Armour, 1/3 Elf Bows and Heavy Armour) with around 200 points of Fiefdoms, something like Forlong the Fat, with 2/3 Axeman and 1/3 Rangers of Gondor/Blackroot Vale.
If you went for Numenor you could take Isildur or a Captain, 2/3 Spearmen and 1/3 archers. As long as one force can volley, you will be fine.