Yea, b/>b means either b or >b, but not both. I did that to try to be less redundant.
You can insert a lot of supports into the supportless combos as long as there isn't a lot of pushback or it's at the end. It's best to experiment yourself.
b/>b y+Dio 3 ^y (select the player to target as soon as ^y hits) b y ^y x [134 damage] b y+heppokomaru 3, ^y (support hits) dash >b y ^y x [120 damage] (actually, this one is hard to time, so not practical) b ^b ^y sanosuke 2+x [~90 damage] b >b y+kurama 2 ^y x b y ^y x+(kaido 3/hiruma 3/others)
The hold supports all work (if not all, then most). That includes shishio 2, You can substitute Dio 3 with other things too.
Not really a combo, but if opp is guarding, you can use >y+buffaloman 2 (I'm not saying start with >y, but use support at same time if they're guarding or for more damage). This is because 1)They can't push guard the >y, 2. button mashing the >y covers the startup lag of the support, and 3. buffaloman 2 guard breaks.
You can also try to loop/semi-infinite with >b y ^y [repeat]. It's not an actual loop, but it can work if opp has wasted their jumps or something like that.
b/>b y+Dio 3 ^y (select the player to target as soon as ^y hits) b y ^y x [134 damage]
When using this Dio 3 combo in training, after I use the second ^y then use X, there is a slight pause and the combo restarts. Meaning after using all the attacks up to the second ^y, it is 13 consecutive hits, but when the special hits the number resets to 0 and continues on from there.
Does this mean if an opponent wanted/tried to, they could jump away?
You should notice that just the regular b y ^y 5x resets the damage counter after ^y.
It means that the opponent is in their static or standing position, so yes, they can try to jump or fast fall if they want to. It should be noted, however, that it won't matter if the next attack is fast enough such that they don't have enough time to jump/guard/get out.
For example, Nami b >b y resets damage counter after >b, but it is universally accepted that it is still a combo. The opp is still for a split second right but they cannot guard fast enough for the y.
Similarly, Muhyo and Fuusuke have that problem. I don't know why the cpu doesn't guard between Muhyo's b and >b, but it can be guarded. And Fuusuke cannot combo ^b into ^y without extra stun or support (it IS escapable) because of this.
With respect to your question, I'm going to say no, but I may be wrong. I don't think the opp will have enough time to escape. I've escaped before and only got hit by a small bit of the beam, but I don't think it can be done consistently.