I came up with a few variations for the bearing design. I shared with a few fellow forumers for feedback and viability. Thanks, guys, for your valuable feedbacks.
The critical parameters - in my opinion, and as per feedbacks from others seems to be:
1) accuracy of machining the parts - since the accuracy of the mating between the bearing and the bushing will decide how quietly and smoothly it operates.
2) length of bearing and bushing assembly: the stock bearing has about one-and-half inch length. This is sufficient to support the 8 lb platter without undue stress on the bushing, which is the softer of the two mating surfaces (the other being the bearing which I think is made of hardened steel). I have decided to arbitrarily use about 4 inch length.
3) design of load bearing part: the stock bearing has a conical cutout at the bottom of the bearing into which the 5 mm ball rests. Below the ball is the thrust pad. Below the thrust pad is the steel "coin" that provide further mechanical support to the pad above. Finally below the "coin" is a circlip lock. This arrangement is good enough to prevent oil leaks from the bottom.
When the ball is inside the cone, about 1 mm of it visible, meaning about 4 mm of the ball gets "immersed" into the cone. The roof of the cone is cleverly extended to act as a reservoir for the lube. No need for sintered bronze.
4) Lubrication: I wanted to avoid using a ball as the interface for the bearing and the thrust pad. This is mainly to simplify the design. So I rounded the bottom of the bearing. My thought was to use a stainless steel as thrust pad and bottom support. It will be threaded as I could not come up with a design that will be leak proof without the use of additional rubber bushing. The rounded portion of the bearing will sit directly on the stainless steel pad. The lubricant would now assume greater importance as it needs to lube hardened steel and stainless steel. My thought was to use (for the bottom of bearing) a mix of lithium grease and sewing machine oil (or compressor oil, if I can source it locally), to obtain a viscosity/consistency higher than sewing machine oil but definitely lower than grease. For the vertical portion of bearing-bush contact, I thought regular sewing machine oil will be better as it has low viscosity. Also, I have been reading up on lubes and the conclusion seems to be that there is no such thing as a universal lube. Each turntable has a different recommended oil.
After 3 iterations and variations, I decided to simply copy the stock bearing design, with the only difference being a thicker bearing diameter and longer spindle. If my regular machinist turns out a good job, other designs shouldn't be difficult to implement.
I have put the design on paper, right down to every last dimension. I will go meet my lathe guy today or tomorrow. Cutting off a 100 mm section of the brass pipe (16 mm inner diameter and 25 mm outer diameter) this morning was hard work. Now I know just how hard brass is. Hoping that this works out well.
After all this, I did an image search for the (in)famous Jeremy bearing and the design of the load bearing part closely resembles what I came up with. The difference being that the Jeremy bearing's rounded bottom is narrower than my design. I guess this is a validation that my design will work as there are already lots of Jeremy bearings doing duty on Lencos worldwide. I won't be able to replicate the bling factor of his designs, though