A suggestion from the Mozilla Russia forum: allow subscription links that add a static list of filters rather than an automatically updated subscription that needs to be hosted somewhere. This is already possible using data: addresses, e.g. Subscribe to two test filters.
Some enhancements to make this feature really useful:
1. Improve https://adblockplus.org/en/abp_linkfactory to allow specifying (or uploading) a list of filters instead of a subscription address.
2. Make subscription dialog show the filters rather than the obfuscated data: address. When the user adds a new subscription himself (via Add filter subscription / Add a different subscription) - allow choosing between the address of a remote subscription and a static list of filters.
3. Make sure that automatic updates are always switched off for data: subscriptions, those are a waste of CPU time.