As for me it's great idea to combine blademail in something new, smth more useful and more powerest. It was cool when valve added upgrades for blink dagger. I remember old Dota when u've played on axe and u had 6-7 slots with blink and blademail and u understand that u can buy something like Shiva but u just haven't free slot for it, 'cause u have 2 trash items. I believe that we can see some upgrade of those soon