And go back to older editions? No thanks, not for me. Feel free to go for it if it suits you and yours, though.
For the most part, it does make things more like 2E AD&D and some older rpg rulesets from the 1980's.
In 2E AD&D, the to-hit d20 roll number for a hit from a fighter attacking a monster with a particular AC_desc (descending AC) is:
21 - level_fighter - AC_desc
(THAC0 for a fighter is 21 - level_fighter).
Changing the AC_desc from descending to ascending AC_asc (ie. AC_desc = 20-AC_asc), the to-hit d20 roll number for the same fighter attacking:
1 - level_fighter + AC_asc
In the case where AC_asc scales approximately as ~ level + AC, where AC is an "intrinsic" ascending AC stripped of the level dependency and/or magic enhancement, the to-hit d20 roll number for the same fighter attacking becomes:
1 + AC + (level_opponent - level_fighter)
which is almost identical to my previous proposal. (One could eliminate the 1, if AC_asc is redefined as being 21-AC_desc).
Now that I think about it more, this d20 to-hit target number of
1 + AC + (level_opponent - level_fighter)
is similar in to how things are done in the Chaosium Basic Roleplaying system, if the percentile dice mechanics are converted to a d20 for the Basic Roleplaying resistance table.
An older version of the Champions rpg Hero system also has a similar mechanic with a (level_opponent - level_fighter) type adjustment. In the Hero system, a hit is rolling 3d6 less than or equal to:
11 + (OCV_attacker - DCV_defender)
where OCV_attacker = attacker's DEX/3, DCV = defender's DEX/3.