Nyktophylax has a nice Tremere flavour, but it gets less useful the more people have it, until you reach the extreme of everybody having it to absolutely no benefit.
I'm going mad. Or possibly blind. I'm sure I doublechecked that he didn't have Skilled Parens before I made that comment, and yet there it is. And he's spent the xp from it, as well.
Agreed the Vallation spell is quite high level (Wall of Protecting Stone is easier). Obviously neither of them are permanent rituals, so neither of them are directly relevant to CrTe fortifying the covenant - but right now, whilst all Tremere want some martial capacity, your magus is coming across to me more as "Terram combat specialist" than "builder". This may be less relevant if you're planning to advance him past gauntlet focussing him more on building things.
For reference, there's a copy of the letter Gregorius sent to the local Exarch requesting the assistance of an architect here: Card & Board Games ARCHIVE & LINKS