I think it's possible to perform my left crankcase cover modification on the TW200.
However, most TW200 owners would disagree.
The left crankcase cover on the TDub has a bearing which supports the bike's extra-long countershaft. This bearing is also lubricated by a small oil passage in the left crankcase cover. Therefore, if you section the crankcase cover, you will need to plug the oil galley leading from the front of the cover; however, I don't see any reason why a sealed bearing wouldn't perform equally well.
However, there is another, more serious factor to consider.
The two, or more, bolts you use to attached the rear section of the crankcase cover must also be able to support any loads exerted upon it by the drive chain. However, the main countershaft bearing inside the engine is also helping to support these loads.
Therefore, I think the crankcase cover modification is possible. Nevertheless, if the loads from the drive chain are too great, you could damage the main countershaft bearing in the engine, which would require you to split the crankcase for repairs. 8O My Zong employs a shorter, more conventional countershaft, so I didn't weaken the countershaft support when I sectioned the left crankcase cover on my Chinese clone.