I don’t have all the same issues as the OP, but enough to warrant a response.
Quick Background
We use HubSpot Tickets a little differently than other companies I’m sure. We essentially use the Conversations / Tickets tool as an order system. People email us at orders@CompanyName.com with the details of their order, we enter it into our ERP and send them back receipts and other documentation. This documentation (art proofs, sales orders, invoices, etc) are all added directly into the email replies as an attachment.
While this situation is a bit unique, I’m sure that other companies have the need to send back and forth multiple attachment files via the tickets tool.
Other Note
If anyone has solutions to these problems that works now, or if I am missing some feature, please let me know. I would love to have solutions to these issues rather than wait for HS to address.
Problem #1: Cannot easily reattach previous uploads
Here is the scenario. We have received an order email to our conversations inbox tool which has created a ticket. The CS rep has responded to the email with an order attachment and proof to approve. If the CSR does not hear an answer after a few days they need to re-email the client to ensure they can approve the order.
Currently, when the CSR is following up, they need to download the previous attachments from the ticket, before reattaching them to their new email. This is because they cannot directly select the attachment already on the ticket for their email reply.
—They cannot drag and drop the file from the attachment area to the email. 
—They cannot select *attachment icon*, “Choose existing” and select a file from the list of attachments already on the ticket.
Additionally, after a few days we alert our sales reps to follow up on a ticket if we haven’t heard from the customer. When they follow up they (again) need to download the files that are already in the ticket, then re-upload them to the email again.
The ideal solution for us would just be to add another option to the attachment icon that says “Choose existing attachment” which would pull up the attachments already on the ticket. You could rename the other “choose existing” to include “document” (see screenshot)
(Side Note - I’m not sure if all these files we are downloading and re-uploading also causes HS to need to double or triple the file storage required, but it might be. All I’m saying HS Team is think of the data savings and implement this feature soon 
BUT - Why don’t you just forward the previous email?
We tried that for about 2 weeks. Of course it does work to keep the same attachment. Replying to the email removes the previous attachment.
HOWEVER, it appears when an email is forwarded (and if the customer actually responds like you are hoping they will), it breaks the automation around moving tickets. Basically the ticket does not move to a new status, it will stay in the “Waiting on Customer” status column and not move to “Waiting on us”.
It’s possible this has been fixed by now, but when we addressed this with HubSpot there was no fix date determined.
BUT - It sounds like what you are trying to do you could do with the quotes / sales tool? Could you use that instead?
I have looked into it and would deeply love for it to work. The overarching drawback is the sales / deals object seems to be built with the assumption that you have individual sales reps going out and getting individual (big) sales / deals. Our workflow is different in that we have a general mailbox (orders@CompanyName.com) in which all orders come. The sales reps help manage the relationships, but only occationally get involved on individual orders.
So since the sales tool / deals object cannot be hooked up to the conversations inbox, it becomes extremely awkward to use the deals object / quotes tool. In addition, I believe (but am not certain) the deals object would have the same draw backs in terms of attachments as the ticket object would have. Since we won’t be creating quotes in HubSpot the same restrictions would apply. (Unfortunately our catalog / products are far too complicated for HubSpot).
Problem 2: File Properties that you cannot use within HubSpot.
It appears the file property field can only be populated with an actual file if it is submitted through a front-end form. Although I’m sure this was done to create more functionality for the front end form experience, it leaves the back end wanting. In the backend, this field just appears as an open text box. The field can be used in snippets, but it will just place the open text information in.
For our use, we would love to create custom properties on the ticket called “Art Proof” and “Sales Order”.
On the left hand side of the ticket, the ticket property would be displayed with a button called “upload”.
When the file is uploaded a few things would happen:
(1) The property field would be updated with the name of the file “file-name.png”
(2) The file would be added to the attachment section
(3) The file in the attachment section would show a tag referring to the field in which it is associated (see screenshots)
Note - I just did “---- sales order” cause I didn’t want to code up an actual button. I just wanted to show placement and property name.
*Note - I just did “---- sales order” cause I didn’t want to code up an actual button. I just wanted to show placement and property name.
Then, if this property is referred to in Snippets / templates / etc, the file would be linked just like a normal document. The file name would appear with a hyperlink to view the file online.
Alternatively, the CSR could attach the file using the workflow described above.
If / when a CSR needs to update the file in the future, they can just “X” the current file, upload the new one and the same thing would happen again. We could then view the details of that property to see if any additional information was updated and when.
