There doesn't seem to be a need to do the current-dir link dance. If one doesn't want to mess with packages (e.g. to ramboot a kernel), it is just necessary to put the proper /lib/modules/$VERSION/ dir and run depmod -a $VERSION before booting it. (We were doing that to for example test usb host stuff)
[ 239.609741] iptable_nat: Unknown symbol ipt_do_table [ 239.609802] iptable_nat: disagrees about version of symbol nf_register_hooks [ 239.609832] iptable_nat: Unknown symbol nf_register_hooks [ 239.610687] iptable_nat: Unknown symbol nf_conntrack_untracked [ 239.611846] iptable_nat: Unknown symbol nf_nat_packet [ 239.613555] iptable_nat: Unknown symbol __nf_ct_ext_add [ 239.613616] iptable_nat: disagrees about version of symbol register_pernet_subsys [ 239.613647] iptable_nat: Unknown symbol register_pernet_subsys [ 239.614501] iptable_nat: Unknown symbol nf_nat_setup_info [ 239.614532] iptable_nat: disagrees about version of symbol xt_register_target [ 239.614562] iptable_nat: Unknown symbol xt_register_target [ 239.614593] iptable_nat: disagrees about version of symbol nf_unregister_hooks [ 239.614624] iptable_nat: Unknown symbol nf_unregister_hooks [ 239.615447] iptable_nat: Unknown symbol ipt_unregister_table [ 239.615478] iptable_nat: disagrees about version of symbol ip_route_me_harder [ 239.615509] iptable_nat: Unknown symbol ip_route_me_harder [ 239.615539] iptable_nat: disagrees about version of symbol ip_nat_decode_session [ 239.615539] iptable_nat: Unknown symbol ip_nat_decode_session [ 239.616333] iptable_nat: Unknown symbol nf_nat_icmp_reply_translation [ 239.616394] iptable_nat: disagrees about version of symbol unregister_pernet_subsys [ 239.616424] iptable_nat: Unknown symbol unregister_pernet_subsys [ 239.616455] iptable_nat: disagrees about version of symbol ip_xfrm_me_harder [ 239.616485] iptable_nat: Unknown symbol ip_xfrm_me_harder [ 239.616485] iptable_nat: disagrees about version of symbol dst_release [ 239.616516] iptable_nat: Unknown symbol dst_release [ 239.617309] iptable_nat: Unknown symbol need_ipv4_conntrack [ 239.618103] iptable_nat: Unknown symbol ipt_register_table [ 239.618133] iptable_nat: disagrees about version of symbol xt_unregister_target [ 239.618133] iptable_nat: Unknown symbol xt_unregister_target