I know the mechanic seems crazy, since it is essentially replicate onto itself. There is a twist, like how you could use the spell. An example of such craziness would be this spell. It may look like junk at first glance. For one, it doesn't do anything if you don't pay the Burst cost. This means it is instantly a 3 mana spell.
So, what can three mana buy you? For RRW, target creature gets +1/+0 and target creature gets +1/+0. Not a big deal. For RWW, target creature gets +0/+1 and target creature gets +0/+1. Another bad deal.
I'm seriously going to promote colour pairing. So... what does 4 mana buy you? For RRWW, three target creatures (which can be the same) get +1/+1. For RRRW, three target creature gets +1/+0. For RWWW, three target creatures get +0/+1. Still only so-so.
Here comes the fun part. What can 5 mana buy you? I'm only going to go through the best few: RRRWW or RRWWW. The result of paying this mana cost to play this spell is that four target creatures get +1/+1. Stacked together, this makes a creature +4/+4 for the low cost of 5 mana with enormous flexibility to spread it around. If you have RRRRW to spare, you could make a creature get +8/+0 for a crazy blitz!.
It gets loads better as we add coloured mana to play the burst cost. Be creative. :D
I put a new fun set of abilities that are something like echo. I'm sure these would have been considered by Magic R&D at some point. Maybe, and most probably dumped due to complexity.