Sorry for confusion
I thought you where after the general split routing term, where you wanted having torrenting over VPN and everything else, e.g. web-browsing etc, over normal connection, though you all along stated what you wanted, and I was just slow in uptake seemingly
Anyway, if just wanting a regular VPN setup and controlling deluge UIs from LAN, then couldn't you just run without any changes? Honest question, and again, I don't know much about networking stuff, besides the very basics pretty much(and some ssh etc, but noob honestly
). I did test this actually, and could connect with deluge GTK client to a deluge server on other PC in LAN and openvpn running also, on same PC in LAN.
In some setups, I believe mostly with split routing, in the sence of e.g. torrenting only VPN traffic, then there can be issues like you suggested, and instead e.g. reverse proxies like nginx or ssh port forwarding is needed, I have read at-least. If you haven't already, there's lots of info herein, though not strictly for your use-case but regardless.: viewtopic.php?t=49883
The post I linked to initially, was because I assumed you wanted the split-routing before mentioned of e.g. only torrenting over VPN, and the rtorrent command to bind to vpn, should instead be translated to the deluge UI or CLI options of binding to network interface. Yes, those options are, as you stated, not for what you initially thought, and are more for binding specific traffic, e.g. in the before-mentioned torrent-over-vpn-only scenario, and/or also can act as a kill-switch at same time. You shouldn't really need it per-say for your scenario, or so i'm guessing atleast, but is a nice thing nonetheless, especially if you not already use other precatuions e.g. iptables rules etc, for proper kill-switch functionality. for mitigating leaks happening through connection drops.
Yeah, as you state, it's annoying as IP changes, so either you have to script it as you also stated, e.g. the up script supports, I believe $4 or %4, cannot remember terminology off-rip, which holds said local IP, and which could be defined to start deluged with -i and -o switch, for in/out IP binding or setting these options through deluge-console. Alternatively, then you could use ltconfig plugin and hardcode tun0 as listen_interfaces and outgoing_interfaces options, but under listen_interfaces option, you should add a port, e.g. tun0:xxxxx, where xxxx is a number for port choosen. There should be no port for the outgoing_interfaces option. If using this method, then that overrides the general deluge networking options of selected port to use, and so should ignore those options + the deluge binding options as you hardcode them directly. You could use tun0 under outgoing-interface in deluge, and just let ltconfig plugin handle the listen_interfaces option if wanted. The reason for that, is that the deluge listen_interface option doesn't support interface names like tun0 unfortunetly, and only IPs, where libtorrent options defined through ltconfig does however(even though deluge sets same libtorrent options behind the scene, but just haden't added support for using interface names as incoming bindings yet, unfortunetly).
Sorry for long babblings and initial confusion/misunderstandings. Also for not really knowing much about this subject in general, and still replying, so if others are in the know, then please jump in and take over, as would be more helpfull to OP.