Profile of Vipper

I don't care about team game balance because it's impossible to balance on a fundamental level due to unfixable flaws. Also Brits suck in team games anyway as far as I can tell, so that's irrelevant to me.

Then you have to clarify that you are talking from only 1vs1 perspective.

In that case is not worth it is probably not worth it unlock both weapon racks and m3 but you can still get brens and BAR-k on other units.

If one check top 200 for last month UKF have one of the highest win rate at 3vs3 with 48.3.

Worth keeping in mind then. Might go look at that since it seems interesting. I don't believe Recovery Sappers can be upgraded with the Heavy package can they?

Recovery sapper can get the heavy sapper upgrade. Even if they could not Heavy sapper can get up to 3 weapons including 3 BAR-K

So are Conscripts and Ostruppen. That doesn't make Sappers unsuitable to be treated as a Mainline style unit when you kit them as one. I'm pretty sure they're worse than both Cons and OPtruppen when kitted out too but that's speculation on my part.

Funny that you mention these units since both have only 1 weapon lost and can not carry 3 weapons.

A single Bren gun is much worse than a 1919 (Reflected via the price and the 2x slot usage) A singular Bren is actually quite underwhelming and barely improves very much about the unit's performance within reasonable combat distances unlike the 1919, it's the second Bren on the IS that push them into being a strong upgraded distance unit hence why most Brit players focus double Brens per Section over spreading singular Brens around.

With bren you pay what you get and it actually more cost efficient than 1919.

You're just objectively wrong here. Splitting your weapon upgrades doesn't provide you enough universal damage to be effective at all ranges, it simply allows you to not be punished for sub-optimal play.

So in other M1919 on riflemen is bad?
So double Bren on Commandos is bad?
Vamp on ober is bad?
LMG or paras is bad?

The only way this is an effective way to kit your infantry is if you're constantly being caught out of position and misplaying your units and even in those situations you're going to be severely ineffective in infantry fights since you can't utilize your maximum damage potential by placing your infantry into a position to succeed. You're doing what is called "Playing to not lose" which ultimately ends up with you losing over a long period of time because you aren't directly countered by anything, but you lack the strength to actually win fights decisively due to the split efficiency. You should work on placing your units in situations to succeed with their maximum potential over attempting to avoid being caught with your pants down.

Actually what it means that will perform good in all ranges and able to position in optimum range depending on what it facing.

If it facing an SMG unit will fight at long distance while being able to deal lots of damage even the SMG unit manages to close it.

If it facing a long range it can move to mid range and be able to trade effectively.

The Fuel requirement to do this makes this impossible in any reasonable game between two players of equal skill. Even if it were possible, it doesn't actually provide enough benefit to justify doing because you're directly contradicting Infantry Sections main strength of superior long range damage by removing one of their Bren Guns, additionally, because you're attempting to also be aggressive with this squad you're invalidating the strength of the 1 Bren Gun on approach resulting in a gimped close range squad that doesn't deal enough damage to justify closing in with and a weaker ceiling in the lack of a second Bren at long range.

Not really, there are modes than simply 1vs1.

Unless I'm wrong, you can only get 2 weapons on the Engineers, both the Recovery Sappers and normal Sappers. Sappers do become durable at Vet 3 but at the point where they are Vet 3 and you've placed double Vickers K's on them they are no longer a supporting Engineer unit. You are using them as a Mainline Infantry Unit and that is okay. When compared to Infantry Sections they're just fine and you're trading a late game infantry performance boost for an early game performance deficient when compared to Sections, not only that, but you're denying the ability for handheld At and Minesweepers for the ability to do this which is a fair tradeoff.

You are wrong heavy sapper upgrade give up to 3 weapons plus armor.

And are not mainline infatry. They are cheap unit with low reinforcement cost and tonnes of utility.

Putting Brens on Raid Sections make no sense as you can simply build regular Sections and place Brens on them for infinitely more impact and better performance. The only justification here I suppose would be the ability to skip Bolster which would leave you with a weakened Tommy + Sapper for not much benefit. While again placing Bren+VickersK on a Raid Section runs into the same problem as with regular sections that you're taking a unit designed with a purpose in mind and neutering that purpose for general utility which is shown to not work because utility does not trump specialized strength.

Your fears are unfounded in any practical sense.

Again not really, its like saying that putting lmg on Riflemen makes no sense. LMG on Riflemen work great.

It actually does. They can fight longer range unit better and still be good at mid range. In sort the unit instead excelling in one range it becomes good at all range.

This is more important at MGs or ATGs which are more likely to get targeted by small arms fire of infantry. If mortar gets targeted by indirect fire you will still get a small survivability boost vs alpha strike damage (the damage over the time you need o react and retreat or relocate), but on the downside it bleeds you more. You are more likely to loose multiple soldiers to a single attack. So there is a downside to sixth man mortar crews you may not have thought off.

If, in your opinion, there is important down side, in having 6 men crews for your mortar, here is tip for you, do not reinforce you mortars to full and leave them at 4 men.
It is an option after all.

In order for ST to work as SPG it would need to role change.

Instead of squad wiping machine it would have to redesigned as for more utility and wiping power.

Change could include hard cap on killing entities, temp circuital vs vehicles infatry/support weapons ability to heavily damage structures, critical damage on emplacements, more consistent fighting capabilities without firing rocket.....

One has to start by moving ST to another commander.