custom separate trading accounts

[gnucash.133518b at telus.net]

I have two separate reasons to enable GnuCash trading accounts. The 
first is because I have bank and expense accounts in two different 
currencies and wish to benefit from the advantages documented by Peter 
Selinger:

   http://www.mscs.dal.ca/~selinger/accounting/tutorial.html

The second reason relates to investments and derives from the section in 
that document entitled "Realized and unrealized gains and losses". I 
happen to live in Canada which uses the adjusted cost base method. To 
quote Peter, "in the adjusted cost base system, it is possible to 
calculate the amount of the realized gain or loss without looking at the 
entire history of purchases and sales. ... you will discover that the 
adjusted cost base at any given time is exactly equal to the CAD portion 
of the trading account. ... the trading account precisely mirrors the 
historical cost of shares. The realized gain or loss of a sales 
transaction can therefore be calculated simply by looking at the trading 
account balance just prior to the sale. Of course, this only works if 
there is a separate trading account for each kind of shares owned". I 
believe it would greatly simplify ACB calculations for me if I can 
implement those separate trading accounts Peter speaks of.

GnuCash automagically creates and populates whatever trading accounts 
are required. This is very convenient, but it does NOT create separate 
accounts for each kind of share and its corresponding currency. For 
example, no matter how many different investment accounts might hold the 
Canadian SHA share, all will automatically use these same two trading 
accounts, namely Trading:TSX:SHA and Trading:CURRENCY:CAD. Moreover, 
Trading:CURRENCY:CAD is also being used for simple CAD/USD expense 
transactions. What this means is that Trading:CURRENCY:CAD is of no use 
to me in determining the current ACB for the SHA shares in any 
particular investment account because it aggregates everything.

Instead of using Trading:TSX:SHA and Trading:CURRENCY:CAD, what I really 
need is for Assets:Investments:ThisStockAccount to utilize something 
like Trading:ThisStockAccount:SHA and Trading:ThisStockAccount:CAD. It 
would be great if this was a configurable item, but it doesn't seem to 
be (feature request). It does seem I can manually create those separate 
trading accounts and then manually modify each transaction to use them, 
but before I commit to that path I would like to know whether there are 
any pitfalls in doing this, especially since I don't know how much 
automatic behaviour is behind the trading account implementation. Any 
typos or errors in entering a transaction like this have the very 
irritating side effect of automatically tossing in an extra pair of 
Trading:TSX:SHA and Trading:CURRENCY:CAD splits that have to be manually 
weeded back out, but I'm hoping this is survivable. Are there any 
reasons why I will regret manually forcing custom separate trading 
accounts like this?

Carl