To pre-empt failure of the sprag starter system, you can remove the primary case(both outer and inner) from the engine, and remove the backplate from behind the "hump" where the starter motor goes in. Then withdraw the whole intermediate gear cluster with shaft from the housing, complete. Then put the back plate on, and re-assemble the primary and parts on to the engine, and you will have a kick-start only bike which has a good sprag that you can put back in to the housing at any time in the future. This retains the "e-start" look.
To retrofit the older kick-start only primary case, you can try to obtain a KS inner primary case which is designed for 5-speed left shift bikes. They are pretty rare, but they are around. The last time I saw one, it was $185 for a new one. The E-start outer primary will work with it, so you don't need to buy a new outer primary case. With this KS 5-speed inner primary, it allows a straight bolt-on of the inner primary with all the normal holes lining up for the bolts, and all the holes in the primary for the left side shifter shaft to go thru it.
If you can't find one of the KS 5-speed inner primary cases, it is possible to retrofit an older 4-speed KS inner primary. But this requires you to drill and tap three new holes into the engine case around the crankshaft seal, because the old type uses a different bolt pattern. This is possible, and quite a few people have done it. It's a little more difficult and scary because you have to drill and tap the engine case, but if you are careful it is not a big deal. Just let us know if you are going to do that, so we can advise you. Then, you have to either switch the gearbox to right-side shift, or else you have to drill the inner primary for the left-side shifter shaft, and also machine it for the oil seal.
We have done all of the above on various bikes. We are experienced in all these processes to convert it in these various ways.