(1) Karma and reincarnation would not pass Occam's razor compared to even simple belief in "cause of all causes" type God, or a deistic God.
Furthermore, Occam's razor is not a "rule" to be obeyed; it is simply a guide as to which alternative to follow when presented with alternative theories that both equally address the known facts, and the one to follow first is the one that makes the fewest assumptions.
(2) Karma and reincarnation have more assumptions than simply the notion of God as original cause.
So you would also be forced into accepting that, of a given species of animal, some would have souls and some would not? How would you be able to tell them apart?
(3) How does the notion of limbo "violate" Occam's razor? All you seem to be doing is cherry picking an assumption that one notion has that the other doesn't and claiming a violation, yet ignoring all the countless assumptions made by either theory up to that point, and furthermore you are making an assumption that the theory might not actually need... For example:
(4)Why should there be a special place called limbo compared to just a bodiless soul inhabiting the same plane as the body? You mean just like prison operates on a FIFO basis?
(5)If you cherry pick a single notion for comparison without examining what gives rise to the notion in the first place, then perhaps your argument holds water as to being more "straight forward". But there can still be a God associated with beliefs in karma, it does not operate in isolation to assumptions and beliefs similar to those you might find in Christianity or other religions.
But again, I am not sure you quite appreciate what Occam's razor is, especially as you think things "can be consistent with" it. It is merely a lens through which to compare competing theories. To look at a theory chock full of assumptions from the get go and to then claim it "can be consistent with Occam's rule" displays a lack of understanding, I fear.
On (1): Agreed that Karma / re-incarnation like Christianity, and most religious do postulate an immortal soul (some "person" that survives death). They differ in what happens to the soul after death. Thus their Occam razor violation count is both one on this fact, but for Christianity it is 2 as Christianity postulates at least a "heaven" exist for soul, no longer tied to the dead body to go to. Actually most postulate a hell too and some limbo, bringing the OVC (Occam Violation Count) to up to four more than the one both have. (The postulate with zero evidence of an immortal soul)
I of course agree Occam's rule is not a true rule, just a guide: Chose the system with lowest OVC.
On(2): No they are equal in their OVC 1 = 1. Christianity and all other religions don't stop with just assuming a creator of the universe. They give him many assumed attributes: For example that he gives a shit about what we do, has many main guiding rules (10 for Christians) we are to obey, has a place called heaven, for which there is no evidence of its existence, where we get to go after death; (if we were socially useful and more places with zero evidence if we were not).
Re-incarnation also has place for us to go after death and there is abundant evidence it at least exists. You assert that re-incarnation makes more unfounded assumption than the one it shares with others (existence of an immortal soul). Name one, which is not also part of Christianity.
On (3)&(4): Some versions of re-incarnation which only allow re-incarnation into new born humans, as I discussed, do have an imbalance between number of deaths and births problem; but I agree the limbo that solves it does not need to be a real place - it could be just the name for where the immortal souls are while waiting for a body to be born they can attach to. The version of re-incarnation I prefer, avoids need of even a non-existing limbo (one lower OVC) by using animals as their waiting place (Animals do exist, we know.) That does mean the number of animals with souls is a variable, but as you say: “How would we know?” Even some “humans” may not have a soul - they are "Philosophical Zombies." and we can't know if they exist or not as by definition PZs behave exactly as humans with souls do.
On(5): Yes, I agree there could be a god associated with Karma/re-incarnation, but assuming that increases the OVC by one.
How is the re-incarnation "a theory chock full of assumptions from the get go ... " Again
I ask for an example of even one unsupported assumption it makes which Christianity does not also make. The OVC of Christianity is huge - It assumes without any evidence: the existence of heaven, hell, often of limbo, saints, angels, the devil, miracles (in large number, each adding one to the OVC) with the "virgin birth" a special miracle and that God has dozens of characteristic in addition to being the creator of the universe.
I follow Hawkings and many other great physicists with the POV that the universe, with still zero total energy (dark energy is negative and with the positive forms makes the total zero) is the result of a brief statistical fluctuation, like on a much smaller scale, is constantly creating out of nothing electron positron pairs in the vacuum of space.- It "inflated" so rapidly* that the dark energy, with the postive energy matter, did not like the virtual electron positron pairs, return promptly to nothing.
* Space expanded thousands of times more rapidly than the light speed. (No matter can move faster than light, but space expansion is not so limited.) That inability of the negative and positive matter to “keep up” I suspected is why the universe, unlike virtual electron positron pairs, could not mutually kill each other to restore the “nothingness” they came from - but I am in way over my head (mathematical ability to offer support), with this idea.