I'd agree that wandering all over Amn, buying equipment, romancing, etc. while Imoen suffers is crap roleplaying, and posted as much. Once the party lands in the Underdark without good equipmen, all it takes is one "wrong" turn to kill them all and force a reload; that too is crap roleplaying, which seems to be what you are trying to avoid by imposing the time limit in the first place. The only ways around that are;First, I do support the idea of making getting to Imoen CHARNAME's top priority. However, one concern:
The party may be be seriously underpowered for the Underdark and the second Bodhi battle if they rush to rescue Imoen ASAP, especially if they have other mods installed. Saying "Well then come back and do the Underdark quests later" is a cop-out; it requires the player to use out-of-character information to guide the character's decisions. That's the kind of weak role-playing that the Imoen time limit is meant to avoid. You might want to consider making the Beholder and Mindflayer lairs inaccessible until the party reaches a certain level, or giving an item reward for getting to Imoen early. Perhaps Irenicus found a large number of confiscated magic items in Spellhold, most of them potions and protective scrolls, including Protection from Magic (for the beholder city) and plenty of potions of genius and defense (for the mindflayers). He still hasn't sold off the equipment if you get to Imoen in under X amount of time, but if you take too long he found a buyer and the items are removed from the game (or show up in the hands of a merchant later in the game).
Nonsense. It is out-of-character information that allows the player to buff up, complete a romance, buy new equipment, etc. Without knowing this were a game, no true friend would spend a month completing minor errand runs instead of dashing after their childhood friend.
You've got it arse about face.
1) Player just doesn't take the low level party into the Beholder and Mindflayer lairs, relying on out of game info to make that choice.
2) You as the mod-maker block those areas to low level parties. No out of game info needed to allow the party to survive.
3) You as mod-maker provide them with enough equipment to take on those areas and survive; I suggested potions and scrolls, as those items are less likely to cause ballance problems down the line. Slightly cheesier than just blocking the areas off, but less cheesy than forcing the use of out of game info.
If you intend to stop one form of bad roleplaying (leaving Imoen to rot), good for you. Why force a different form of bad roleplaying in the process?