I don't know about 30' being the ideal length for Solo liveaboard but I think that's a personal choice. I can only speak from my experience on my Island Packet 37 who serves me very well. I am 6'2" as well and people were laughing at me, when (on boat shows) after examining the cockpit and deck layout, my first look was in the head. I don't like to shower bend over or sitting down showering and that did eliminate quite some boats for me.
In regard to blue water cruising IMHO up to a certain size bigger is actually better and will give you (everything else the same) a more seaworthy and more sea-kindly boat. When I stepped up from a nice 30ft Hunter (bought strictly for coastal cruising) to my IP 37 I couldn't believe the huge difference. 15 to 20kts winds are now pure fun and have not been before.
I am contemplating to take my IP across oceans in 2 years when I retire, unless I exchange her bevore for a moderate size catamaran I am thinking about as well.
While I would like to sail with crew/companion I am setting everything up to be able to single-hand. I haven't crossed oceans yet but cruising Tampa Bay to Key West direct or being offshore about 150 miles in the Atlantic when I sailed from Florida to the Chesapeake this summer have been pure bliss.
I am sure you will find a good boat that fits you well both in size, style and handling. There are many folks out there single-handling moderate boats (35' to 40') and I have heart about a guy who does it on a 46' boat. I think it's about your personal comfort-zone, your skills and your expectations. I sail my IP 37 almost every weekend, and most the time solo or with non-sailing friends (much harder the singlehanding
I have a lot of fun solo on my 37' boat but I guess I would be a bit uncomfortable on something much larger than 40'.
I don't know where you live, but should it be somewhere close to Annapolis, please by any means join me one day and observe on a "singlehanded" day sail.