I personally think this rifle has way too many variants to be the same rifle. The internal mechanism for a laser, block, rail, and case-less sabot are entirely different. While I understand the intent of making this weapon universal and used in many applications, I feel that it goes beyond the realm of reasonableness.
A Simple and Reliable internal system that requires almost no maintenance, or change
The Ability to change the internals to change the capabilities of the weapon in any Form
The last two goals listed above are in extreme conflict with one another. You’re saying that it’s so simple that it requires no work but then you are able to change the entire function of the weapon. By the very nature of the ability to change functions means the weapon won’t be simple. There isn’t any example of a weapon I know of that is both able to rapidly change its internals and maintain a simple and reliable design.
The only weapon that I think is close to this is the AK-47, but gains its fame for reliability because it actually is simple. One doesn’t rapidly change the function of the AK-47 using the same weapon. It fits the Assault Rifle role and only that role.