Hi TT,
First piece of advice, which ever measurement you decide to go with, be it Metric or Imperial, stick with it (I know that you know this). Because most of us on the forum are Brits, metric will be the measurement of choice I'm afraid.
As for choosing a base, I really wouldn't get too hung up about it. Plenty of onions, minimal spicing, that for me seems the way forward. Make enough so you can freeze it in individual portions of about 300ml or 0.634 012 925 66 pint US Pints ;D
As for voting for a best base recipe, we have chatted about this in the past and I think that we agreed that it would be quite difficult to attain which would be the best. The trouble is, In Britain, we have such variation from region to region, a bit like our accents. It can really change from town to town. What may be great for Mancunian curry eaters, could be utter rubbish for our Glaswegian cousins, and so, a conclusion is a mere pipedream.
We have however, set up a panel of "recipe testers" whereby we pick something simple every couple of months, such as Onion bhaji for example. We pick 5 or 6 recipes and 5 or 6 of us road test them, and see what, in our opinion, delivers the best in, taste, ease to make, cost and texture. You may want to keep an eye out for this but I think we're a very long way off from doing bases and mains.
Ray

P.S, Here's my base
https://curry-recipes.co.uk/curry/index.php?topic=4596.0 ;D ;D ;D lol