Custom fields for HTML personalisation - thoughts/questions

I'm currently using CM to send out an email to our customers, but I would like to add a high level of personalisation to each email.

Essentially there are going to be two large blocks of HTML in each email which are going to be different for every person.  I am thinking that maybe I could use CM's custom field feature to implement this, but was thinking:

* We have ~2500 people on the list at the moment, how feasible would it be to update the custom fields on all of these once per month?  Does anyone else do this?
* I am assuming that the custom fields are HTML-escaped?  Ideally I would like to just include the HTML from my system via a custom field, an "HTML" type would be very cool here, with the option of providing a plain text version too.   How do others achieve this?


Ross :)

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