Horwath
Legend
if abilities do not increase then 18 STR will only be a problem at levels 1-3. that you go through within 2-4 sessions.I could see half-feats to make uneven scores even. Other than that, having a higher array would be possible. I think however that an 18 at level 1 is too much.
But then we should dissociate attributes from everything besides skills (as you suggested otherwise) and few othere things (which I would suggest).
At least we should not expect stats to increase at all.
Maybe Str as requirements for high damaging weapons, dex for light armor cl (you can circumvent the requirement with heavy armor), con for hp, int for bonus proficiencies in tools and languages, wis... maybe Initiative (as initiative nowadays is more awareness in the first round of combat) and cha for attracting followers...
and having no ASI's across levels and all abilities being even, or even better, just use modifiers and point buy modifiers, will remove problem of meta-gaming with planing your abilities in advance.
Just pick your abilities at 1st level and that is it.
And hope for some magic items.