I think that they are the only way for now. As Ukraine isn’t part of NATO, troops can’t be sent in from the west without causing HUGE problems. The difficulty is going to be about finding a balance between putting enough pressure on to make Putin step back from the brink but not overdoing it to the extent that he will over-retaliate. If China gets involved in some way I think that this might help because it seems to me to be Russia’s most powerful backer. It is obviously way too early at this stage to tell but I wonder if China will get concessions from the US, Europe and UK (e.g. lift various restrictions/tariffs) in order to get Russia to the table. Then you could have Ukraine becoming a member of the EU but not NATO perhaps. This would help Ukraine economically but also keep China and Russia happy about not expanding NATO. NATO countries could, however, pump money into Ukraine to help them make their own forces better whilst also upping their own defensive budgets, like Germany for instance.