Which issues?
Do you see me flaming?
The process you see is what it is, the rails are sanded a bit before. I challenge anyone to do it faster and more feasible , cleaner, etc etc.
You can do 1,2,3 with PU. Actually, the epoxy is brittle. The elongation break for epoxies (cheap ones), is way less than PU (shore 90). The PU gives you impact protection as per production boards. Not to mention cost coz PU is way less expensive.
How many bubbles you've got in the rails? That's probably more near wood line simply because this is where air is trapped and degassing (epoxy produces heat, heat will expand air bubbles). There is no way to control this. The air void can be trapped inside no matter what.
The premade PU rails eliminate this, as you see, it's very tight channel. For sure I'm using similar for inserts and fins.
And, it is highly repeatable, which diy pouring is simply not. Forget about the abs, it's too expensive and too much work.
D.