If you let them alone they will die quickly ! even in the game do not worry .They were not meant to be able to survive on their own or fight on their own and we don't read of them roaming the battlefield in their own right.
But why is everyone so obsessed with those units . there are usually no more than 2 or 3 units . They are costly and their role is to support cavalry . if someone uses them as muketeers ..a musketeer unit is cheaper and does the same work . If they all have attached guns they are even more costly . Are hey the superman units of the game . I do not think so .
I am beginning to think that some people just want to get rid of a unit they do not know how to handle .
Rules are rules, and all rules have a problem somewhere .
Were the commanded shot with regimental gun very efficient ? if yes, the rules are perhaps doing a good job because everyone seems to fear them . So the result is there even if not "logical" . Were the commanded shot with regimental gun not very efficient, not really better than without canons ..ok let's change the rules and no regimental gun .
Now people ...for the guys who have time and swedish and german sources ...go and study the battle of Lutzen and all other battles to compare the details .. It's the only way to fnd out
I might get some swedish information but you will have to wait a few more month, even a year or so !