I understand that there is a need to "smooth" out the transition to the new omega item, but I am really wondering how much effort should be spend in streamlining items that will be not available anymore and should become obsolete fast enough (if the new system achieve it's goal).
Why not just remove the +power altogether and call it a day ?
For us player, such clarity would mean that already today we could plan which all hero or specific hero unique we would like to keep, chase, reroll accordingly.
I guess already taking care of all none unique items that have +power and will need conversion will be a huge job (as it will be scrutinized by the players). There as well, you might just want to call it a day and just remove altogether the +power.
Doomsaw once said they don't want to revisit past items because it's too much work, and they rather concentrate on adding new things. Fair enough, and the overall change could land in the same category.
If it's really not acceptable by the player base to loose all "their hard work"* without some sort of compensation, then I hope the conversion can be highly automated with a script that would check +power and convert smartly.
Something like:
+all power get a coefficient of 21, +all power in a specific tree get a coefficient of 7, +specific power get a coefficient of 1.
Sum the score of the unique and place an attribute bonus according to a define range (maybe divide the sum by 10 or whatever). Check if the unique as a specific damage type and put the attribute accordingly (summon -> intel, phys -> strength, energy or mental -> energy, combinaison of all -> fighting...).
I would really not like to see the first TC iteration be all about discussions about specific items being less or more powerful than before... I think we should learn to let go and be brave, scratching the obvious as clearly as possible and as soon as possible. We will benefit from this in the sense that we could prepare our characters for the new system earlier, and not make a gamble or a power game discussion during the transition phase.
The time should be spend on the future omega system.