Autoland & Cat 2/3 are different things. One is a procedure the other weather conditions. Naturally if the weather conditions are below Cat 1 an autoland is often required; (depends on operator's and a/c limitations).
An autoland on a Cat 1 instillation is allowed, but generally the conditions need to be visual as defined by the operator. The reason for allowing it is to allow the pilots to maintain their LVO currency, and the reason for visual is so that you can assertain before, and at the latest, 200' if the a/c is stable and in a good position to allow an autoland. If not, then disconnect and manually land. I know about the nose up trim, but this is the procedure that has been allowed by all airlines I have worked for.
To fly an autoland (Cat 2 or 3) approach in marginal CAT 1 conditions is to achieve a lower DH. However, this would require the runway to be authorised and LVP procedures to be in place. If the Rwy was so authorised and all criterea met, than this would be sound airmanship and give the best chance to achieve a landing. If the Rwy was Cat 1 only, and the conditons at or near Cat 1, then the best that could be done is a coupled approach to Cat 1 DA and manual landing.
I thought one important point in the spec difference between Cat 1 & Cat2/3 installations was the response time to power loss and switch over to the SBY power systems. For Cat 2/3 the time is an order of magnitude faster than Cat 1.