Can any of the other GL Accounts be changed on Asset Categories that have assets assigned to them?

It appears that Oracle will allow modifications to the Depreciation Expense and Bonus Expense accounting, but all other fields are "locked" on the Asset Category form if an asset has been assigned to it. (Refer to print-screen attached.) We have a user that wishes to change the CIP Cost and CIP Clearing accounts that are established.

Question 1:     Is this form of maintenance supported?

Or, is the only option to create a new Asset Category and re-classify pre-defined assets to the new category if changing those fields?

Question 2:     What is the expected accounting impact of assets after the accounting has been changed for the Depreciation Expense and Bonus Expense? (I assume depreciation going forward for existing assets will use the new accounting after the category has been changed. New assets defined to the modified category will depreciate using the new accounting. Is this assumption correct?)