Our challenges with HP DL380p gen 8: storage space & HBA


We have DL380p gen8 server, and want to use it for hosting some vm’s and for backups.
And we intend to install Proxmox on it and utilize zfs benefits.

What we need:
1- good storage amount = 3.5" drives (we have bunch of them)
2- direct access to drive (to pass them to proxmox/zfs)

The issues:
1- it had 8 sff enclosure, and we want lff’s to have more capacity and better prices.
2- After long testing I coundn’t pass the controller (p420i) to zfs, I did convert it to HBA but no success after that (IMOUU Issues).

Possible solutions:
1-Best solution will be replacing the front panel cage assembly from HP (670944-001) so I could install it in place of my panel (But I want to know if it Possible)
2- I think I must Install a second HBA and connect my internal disk to it to be able to pass it (what will be better: SLI or HP?)
3- If my solution won’t work, I can utilize an old case to host disks and connect them to my server’s new HBA.

1- I know about fans going crazy with some third party parts, and I hope you can help me with that.
2- I am not in the US, so shipping prices are not ideal.

What do you think ?