Equitable charge on sale of property

We have an NRBDT set up some years ago with an equitable charge over the deceased’s share of the matrimonial home.
The widow is now downsizing, but does not wish to repay the debt at the stage and the other trustees are agreeable to this.

The equitable charge route was used for SDLT reasons, rather than any Phizackerley type problems, so I wonder if there is any reason why we cannot now replace the charge with a simple debt arrangement? Are there any tax consequences of effectively releasing the charge in consideration for an iou from the widow? Is it necessary for the trustees to receive the cash, in which case there will or at least may be a tax charge on the indexed increase/interest?

I am struggling to find any detailed discussion of the options in these circumstances.

Diana Smart
Gordons LLP