It would take a serious rework of client code. Maybe if they did like Lam and you download a seperate client.

Because in ddo, the following changes, I think, would have to be made to address the pnp -> mmo differences:
Monsters: reworked completely
How so:
How it seems

Code:
They have basic stats, modified by various elements/attributes.
These modifications are in direct response to the overpowered nature of players.
How it could become
Code:
Move them back to basic stat blocks.
Offer pen and paper progression with the abilities gained from gear and class selections/templates.
Quests: reworked completely
How so:
How it seems

Code:
Tailored to be difficult for a variety of current powered characters.
Rewards commensurate to the ability to repeat.
How it could become
Code:
Linear difficulty scaling, based on quest difficulty selection and makeup of group.
Rewards increased drop rate due to quest only being playable 3/4 times per life.
Loot: reworked completely
How so:
How it seems

Code:
Massive table system to simulate randomness while giving offerings of 'decent' gear.
How it could become
Code:
Smaller, more linear table where most of the 'junk' rewards are turn-in capable for named loot or crafting better gear.
Larger chance to get special loot due to limited run cycles/life.

Stats and player abilities: reworked completely
How so:
How it seems

Code:
SP is an unlimited source of power for casters.
AC is useless for most builds.
Spellpower amps the damage too greatly; Spell crits punt it over the edge.
Stacks devestate most focused builds (abilities, enhancements, effects).
How it could become
Code:
Make spells take rest/daily slots.  Limiting their use to be more in line with Pnp.
Remove spellpower and leave feats like Pnp.  Allow effects to work as written.
Reduce stacks; this will cut down the need for increased basics in all areas.
Combat: reworked completely
How so:
How it seems

Code:
You don't need to see an enemy to hit it.
Enemies react too quickly or too slowly to being hit.
Enemies response to players is erratic.
Combat capabilities do not instill fear or panic.
Enemies don't need to see you to hit you.
Stacks affect combat severly.
How it could become
Code:
Draw distance of enemies based on stats would creat a way to manage initiation rolls.
Client side AI could help mitigate lag in combat.
Removal of stacks would smooth combat speed as well.
Add spell like effects based on combat triggers (damage in one blow, etc).
Overall, ddo and pnp are too divergent in direction to even bring in any semblence of alignment.

If you wanted pnp dnd on the computer, with real time and 3d like ddo; you would lose out on enhancements, epic destinies, and most of the loot. You would potentially gain more prestiege classes, deeper epic levels, and maybe exclusive loot.