How to setup a signature requirement when changing deal stage

How to setup a signature requirement when changing deal stage

Is there a way to set up zoho crm so that it requires a signature from a client when changing deal stage? 

Basically when changing deal stage I have some fields that become mandatory and customer must accept before proceeding, but we also need a signature from client.

I signed up for the zoho sign trial but I cannot find option to make it a requirement.

I understand when looking at the deal you can click on the button to initiate zoho sign but I would like to either make that option a requirement (so that it forces zoho sign document each time a deal is set to a certain stage, or to just have a client signature field in the CRM deals field.

Ideally, having a signature field in the deals module would be excellent. Once that field becomes mandatory, it can appear in the "verify details" popup where they can signand it could either save as attachment or just display on the field  as a png

Is there any work around or suggestions/solutions to this?