With Captain America's heart coupled with the Uni-Power, infusing him with every power, knowledge and battle experience the uni-power has ever been in contact with, as well as his newly aquired power, strength, speed, durability, knowledge, battle experience, fighting ability, energy manipulation, healing ability, raised by 5000 fold, this is his base power, with every shard of the Uni-Force he is bonded with his base is amplified by 50 fold. (see blow for more)
He has the power, knowledge, battle experience, and every ability, of every host the Uni-power has prior bonded with before, not just of the 616 universe, but of the entire Omniverse.
This is no longer Captain America, he is now Captain Omniverse, for he is bonded not with a shard of the Uni-Force but he is bonded with every Uni-Force in every Universe and multiverse, he in essence is the Omni-Force, Captain Omniverse.
Thanos is given one week to prepare, Thanos may seek and try to aquire any item or artifact in the Marvel Omniverse, he may also try to recruit others to his cause, but remember Captain Omniverse has Omniversal Awareness and fights for Righteousness and Justice.
*NOTE*
Write and describe what you imagine Thanos would do, their is no limit to Imagination, no limits, but remember to keep it interesting and deep as in a way making our own story arch for a comic.