First of all thanks @galaxy for your comment here. Glad that someone actually answered, it may help people in future who may need some help in similar issue, instead of waiting hours on so-called active Discord channel or tickets those are only available to direct customers.
And now coming back the topic:
Well, yes I have figured that out already and figured lot more. Its quite cumbersome to manage domains , even how customers are presented with registration process is bare basic, further offering free bundled domain with hosting is not elegant and customer friendly. Coming to brand new domain manager with 5.1.x, is nightmare to configure if you plan to offer lots of domain tlds, almost everything is manual which completely defy the term automation.
Apparently, Blesta and folks have their own path of development where they are completely ignoring the fact that apart of good piece of coding, customer acquisition is the foremost feature of any business and if you are loosing potential customers just because you used some paid billing panel for automation (yes, Blesta is not free, its paid software) which lacks in basic feature for its niche market (read hosting market) then even being cheap , you are loosing more money than you may have saved.
I figured that domain part of Blesta is meant for days when there were 3 main tlds (.com, .net, .org) and couple of more country level tlds , even latest domain manager is lacking apart of multiple of years billing option. I have discussed this in whole lot on other hosting forum and apparently people agree.
I can go writing on and on here as had been heavily investing (and now wasted) my time in understanding Blesta ecosystem from last one month, specially last week. Was hoping to make it my go-to Billing and Automation software for now and future as its also open sourced and dev friendly too, this way can customize when I need a thing or two which is not there. But it doesn't that you spend all your time to make it work your desired way instead of actually focusing on your real business.
I saw people suggesting for improvement those are necessary if you are offering shared hosting with domains but looks like DEVs have their own perspective and are unable to comprehend their customer's point of view. Blesta has got traction recently due to WHMCS price shuffle, I hope developers will change their attitude of forcing their perceptive on users and instead try to understand need of time, and probably in next 2-3 years it will be equally useful for its niche market out of the box without compromises.
I have nothing against Blesta, in-fact was hoping that it will be helpful for us, both in terms of money and usability . Its good if you are not into domain much or you don't care about it, but for most of the small business, versatile domain storefront is must even though domains are not actually profitable part of their offering and Blesta seriously lacks in there. Above that, what Blesta lacks most is lack of open attitude of people managing it, everything feels forced here from the point of view of developers , be it how Blesta ecosystem works, or how they handle support queries or customers.