[Varyon]

I had a few further considerations about this variant last night, so I'll post what I can remember...

Very Low Hits: The tables only deal with hits that are multiples of 5%, meaning other probabilities should be rounded to the nearest .05. However, what happens when you have 1% hits? Rounding to the nearest .05 gives us .00, meaning no hits, even if you were firing a million rounds! In these cases, the best option would be to multiply your probability by something that will make it a multiple of .05, and divide your RoF by the same factor. With the way probabilities work, this isn't entirely accurate, and it also means a reduced spread of possible results, but the average stays the same and results are within error, so it's close enough. With our 1% RoF 1,000,000 example, we could instead go with 5% RoF 200,000, 10% RoF 100,000, 50% RoF 20,000, or plenty of others. With a ridiculously high RoF, you'll want to combine this with the option to have each "hit" be multiple bullets (so go with 50% RoF 20, and each hit is 1000 bullets).
Note you could even use this with higher probabilities. If you have 5% with RoF 20, 50% RoF 10 will give comparable results. You can opt to give your players the option to do this, down to RoF 1, meaning they can decide how much range of hits is there (it's a gamble - you can go with just the straight average, or you can hope for more hits and roll for it, at the risk of getting fewer hits). Your best bet may be to err on the side of drama - if the average number of hits would kill/incapacitate an important character/object, feel free to require rolling!

Walking the Burst: The roll to stay on-target handles this in a given round (because it's possible to compensate well enough to get more on-target), but what about between rounds? If continuously firing a weapon at the same target, you can opt to simply try to keep it on-target each round. Don't roll to hit, only roll for staying on-target, using your MoS from the previous round as the base. Your weapon's Acc bonus may no longer apply - use the rules for Follow-Up Shots and Walking the Burst from Tactical Shooting. So, let's say you're firing a tripod-mounted RoF 30 HMG at an armored vehicle. The first round, you hit with MoS 1, then fail your roll to stay on-target by 3, dropping to MoF 2. The next round, you could opt to try and stay (or, rather, get back) on-target. You make your Walking the Burst roll, allowing you to retain full Acc (otherwise you'd be working at half Acc). Your initial roll is counted as automatically being MoF 2, then you roll to stay on-target, succeeding by 5 and getting to MoS 3. Next round, you could try for the same.
For truly walking the burst (for the purpose of hitting other targets), you have a few options. One would be to simply use the Walking the Burst rules from Tactical Shooting as-is (thus allowing you to just skip Aiming first). Another would be to measure the distance between your first target and your second and convert to SM to determine how far from the second target you start (assume MoS 0 against first target). For example, let's take two humans (SM 0) that are 5 yards apart. You start shooting at the first, and end up at MoS 1 when all is said and done. The next round, you opt to walk the burst over to the second. SM 0 is a 1-yard sphere, so MoF 1 is a 1.5-yard sphere, MoF 2 is 2 yards, 3 is 3 yards, 4 is 5 yards, 5 is 7 yards. You're 5 yards away from a 1-yard target, meaning you're hitting within a 6-yard sphere, for MoF 5. This is where you start.

Reducing Tracking Error: Ask any soldier - for best accuracy, you want to limit yourself to short bursts. Under this system, the reason you want to do this is due to the potential for tracking error - getting off-target during the shot. When firing at less than full RoF, multiply your MoS/MoF on your roll to stay on-target by the fraction of RoF. Thus, at half RoF, cut the MoS/MoF in half, and so forth. In our Walking the Burst example above, let's say the soldier is firing his weapon at RoF 15, rather than the full RoF 20. His initial failure by 3 is reduced to 1.5, meaning MoF 0.5. His later success by 5 is reduced to 2.5, meaning MoS 2.
For dealing with the fractional values this produces, you have two options. One is to simply round (but keep it in mind if you opt for Walking the Burst), so our above MoF 0.5 becomes MoF 1. Alternatively, you can automatically round it up (meaning even n+0.0001 becomes n+1), but weight the result by the fraction when determining average (in our above example, determining average would be [MoS 1]/2.5+[MoS 0]/2.5+[MoF 1]/5).

Hitting the Wrong Target: Even when you are dead-on on your target, you may have some bullets miss... so where do they go? As noted previously, targets are approximated as spheres of their SM (a 1-yard sphere for an SM+0 human). You can determine how many SM's apart a target is from another using the same methodology used for Walking the Burst, and note that this is how many more "steps" on MoF they are from the initial target. Note the outer limits of the target correspond to MoS 0, so start at this point!
Optionally (very optionally), you can opt to roll 1d6 to see in which direction (left, right, up-left, up-right, down-left, down-right) your point of aim scatters from the center. Enemies in the same direction are at reduced MoF, enemies in in the opposite direction are at increased MoF.
Let's look again at the example of 2 targets standing 5 yards apart. Our gunner has MoS 2 against the primary target. Not considering scatter, we reduce this to MoS 0 and find the secondary target is at MoF 5. If we consider scatter, MoS 1 means within a 0.7 yard sphere around the primary target's center of mass. If we scatter in the same direction as the secondary target, this means we're 0.35 yards closer than our original calculation of 6 yards (not enough to make a difference). If we scatter in the opposite direction, this means we're 0.35 yards further away (again, not enough to make a difference). Were we instead at MoF 3 (within a 3 yard sphere) against the primary target, scattering in the same direction would mean we are 1.5 yards closer to the secondary target, dropping range to 4.5 (effective range 5) and thus MoF to 4. Scattering in the opposite direction means we are 1.5 yards further away, increasing range to 7.5 (effective range 10) and MoF to 6.
If targets are at the same height and you roll up-right, down-right, etc, halve difference it makes. Ideally, you should instead roll 1d8 (assuming you have one), allowing for all cardinal directions and their 45-degree equivalents.