Wait and see is a good option, I think we are all still trying to figure out the best setup. Maxing your current item is the way to go, IF you are sure of your setup, since it is hard to change things after imbuing. If you decide you want another legacy, you can't just swap in a new legacy like in the past, you need a special imbued legacy replacement scroll, which is only available for TP, or spend MC I think.
All the exp you have into the item will not be lost, it just becomes the new baseline for the imbued item. You'll want to make sure you have at least a few million IXP runes saved up to re-level the weapon. Same for any star-lit crystals applied, remembrance, delving, etc. That are all factored into the new item, and it's much better to do those before imbuing. Although, it doesn't take much at all to get the weapon back to where it was - the rest just makes it grow more powerful (depending on your class and specific legacies). I would do some more research before committing to anything.
Legacy tiers don't seem to matter all that much when you apply them. If you are at t6 pre-imbue, you start at 31 post-imbue. If you were at t5, you'd start at 30. So it's either add one pre-imbue to get to t6 to get to 31, or add one after to go from 30 to 31. At least that is my experience so far.
This is a good write up:
http://rarebreed.guildlaunch.com//fo...33773#37639769
And check here for legacy changes:
https://www.lotro.com/forums/showthr...81#post7361581
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