I think it was changed because it was pretty easy to get a lot of available AP per turn while at the same time reducing a lot the cost of actions, leading to some serious imbalances when your most powerful skills would only have at worst 2 turns of CD and cost relatively nothing.
It reached a pretty stupid point where a backstab rogue could literally annihilate half the opposing army in one turn and still be able to sneak at the end... I dread to think of what could be done in DOS1 Classic with both Lone Wolf AND Glass Canon ( I didn't go the Glass Canon way mostly because I felt I already had too many spare AP per turn ).
Back to OP, I'd say it may be a solution. On the other hand, everything could also still cost 1 ap but maluses / bonuses could come from other sources :
Less hit chance with 2handed or malus to defense.
More hit chance / inherent backstab capabilities with Daggers.
No close quarter attacks with Bows.
Inherent Attack of Opportunities with Spears.
Better chance to crit with only one single-handed weapon.
Etc.
I feel movement should overall be left alone, as it never is very fun when it takes forever reaching your goal only for it to have already been killed by the ranged characters. More diverse maluses and bonuses depending on the weapons/playstyle you chose could go a long way in providing a fun and somehow more customised experience to the players. It's also way harder to balance, but heh, nothing is easy.
