For merits, SE will presumably let you put 5/5 into one if you so desire. I don't know which I'll do yet as they don't really tell much about what each one actually does or what 5/5 into one will do. But I believe some speculation on ideal 5/5ery is in order.
The Magic accuracy+ ones will likely add more macc+ with each additional merit and at #4 or #5 possibly go down to 1 Stratagem charge in cost. Outside of lolDivine Magic and the white magic enfeebles (Paralyze, Slow, Silence) white magic is great from /WHM and /RDM precisely because it doesn't need to be accurate as buffs/cures aren't resisted. Which makes
Altruism look to be lolAltruism already.
Focalization looks like it could be pretty awesome. Scholar's main shortcoming from a replacing BLMs perspective is problems landing spells on big things. (There's also the no Stun and -ga3 spells, but those are less important generally.) How much will 5/5 Focalization improve magic accuracy though is what I'm wondering. Macc+25 at 1 Stratagem charge cost would be worthwhile and make it a decent candidate for 5/5ery.
Enmity reduction Stratagem abilities look less useful.
Kaeko has made it apparent how useful an Enmity- gearset is with Light Arts. Unfortunately, what he shows that an Enmity- build is useful for is a) Cure IV spam b) AoE buffs. For the former if each
Tranquility merit was Enmity-10 to the -50 cap it would be handy for Cure IV sometimes. But using 3 of 4 charges to AoE Stoneskin or Phalanx makes it pretty pointless. But really due to the other options available anything short of halving your Cure IV enmity with 1/5 merit at a cost of 2 charges it's not worth getting.
Equanimity looks even less useful than it's white magic counterpart. I can't think of any situations where I say "Boy, I sure wish I could nuke more without pulling hate" as Scholar. Tanks are either decent enough nowadays that you can nuke at a decent pace or there is no tank and you can go all out in a solo/manaburn situation. This is like the Muted Soul of SCH merits.
Enlightenment actually looks quite cool. It's in effect a mini-2hr that lets you save your Light Arts/Dark Arts change recast as well as 2 Addendum Stratagem charges to use a spell that's in either addendum with full B+ skill. From the description it doesn't sound like 5/5 will increase it's effect in any way (like Formless Strikes), but rather just reduce the recast on it (like Feint). Following the existing pattern among Group 2 merits that means it will be able to go from 10 minutes down to 2 minutes.
The ability to stay in Addendum: Black and get around the penalties to white magic and use an Addedum: White spell every 2 minutes makes this one of the top candidates for 5/5ery. If you are filling a Curing/buffing role you can pop it and throw out a Blizzard IV to finish some mob off. Or, perhaps more usefully, you can Sleep 2 an add without having to change to Dark Arts, use Addendum: Black (assuming you have a charge ready), and then cast Sleep 2. If you are in a super MP efficient BLM type role, then the ability to toss a Cure 3/4 for less MP or put Reraise 2 back up quickly would be rather handy too.
Stormsurge looks fairly interesting. STAT+3 for the first merit and presumably +3 for each additional merit to a total of +15. The obvious bonus to the Scholar would be to use Hailstorm for INT+15. Running around more quickly with Desert Boots + Sandstorm would also provide a nice VIT+15. For other people they could get +15 to the stat of their choosing as well. Samurais could get STR+15 for their WS, other melees might like DEX+15 for an Acc boost and possibly get bumped up a crit tier. RDMs might like MND+15 for debuffs. Other BLMs might like the INT+15 boost as well. Being able to have an INT+15 boost fulltime makes this another candidate for 5/5ery. (Or it could be 3->3->3->1->1 sort of like Overwhelm.)