Consider and be aware that to threaten the financial existence of a professional person for human error is fundamentally inequitable, and that the appropriate solution is to make sure the professional, your architect, is effectively insured to cover the responsibility they have to you as their client.
If the Institute's standard agreement is not suitable for your project, seek well informed advice in your contractual negotiations with your architect so that the rights and obligations of each are fair, appropriate, reasonably able to be met by each party, and clearly expressed. In particular, your adviser should properly understand professional indemnity insurance, its operation and the terms on which it is available to architects.