Looks good, except for that fourth PzArtBtl (in ArtRgt 100). I think that one btl supporting three maneuver units each (tank + 2 inf in each brigade) should be enough there, especially considering having two RakArtBtl at division level.
The artillery units in ArtRgt 200 would at the beginning receive pretty much anything "left over": FH-70, M110, FH-105; M110 and FH-105 could then relatively quickly, as money permits, be phased out and replaced by more FH-70, so we'll have a single artillery ammo caliber.
The brigade Panzerartilleriebattaillons have their task and the divisional Panzerartilleriebattaillon has another tasks.
Of course the simplest thing that could be said is taht it is better to have that battalion and not need it than to need it and not have it.
But also we have two divisions that automatically leads to the need for corps artillery assets. In that case that are the two Smerch battalions that I have put in the divisional artillery regiment to simplify the order of battle. Otherwise the Panzerartilleriebataillon should stay a single divisional asset and the Smerch battalions form a Corps artillery regiment. That automatically leads us to the question about the Artillery recon battalion. The brigade SPH-battalions are simple, as they could use the brigade ISTAR assets for targeting. But where should we put the artillery recon unit as in that case it should support:
- a divisional SPH-battalion, which is mandatory and not optional for operational flexibility
- two MLRS battalions
- a second line towed artillery regiment of three battalions.
Another point of concern is that MLRS is not as nearly as flexible as SPH-artillery. It has greater firepower, so it is significant to have it But it could not replace SPH.
And you are forgetting that the SPH-battalion could be used independently. To use one of the three brigade battalions means to put it outside the brigade structure, which would drastically lower both its and the brigade's effectiveness.
Another aspect is that you could tailor a battlegroup of a randon number of infantry, engineer etc. units from the second division and the corps assets. In that case if that battalion doesn't have other tasks at the moment to perform it could automatically provide the fire support for it. Because even as we put it the artillery assets in the 2nd division are rather thin, with one towed artillery battalion to 8 infantry battalions.
I think that the number of guns or howitzers in a battalion should not be lower than 18. In that case we fulfill your view for 50 SPHs needed to procure as we already have 18 M109s. Additional 3 battalions of 18 M109s each means 54 units. I really wouldn't like it, but I would compromise in bringing battalion numbers down to 12 units for 18 existing plus 30 obtainable M109s for a fourth towed artillery battalion of 18 units, but scratching the divisional SPH-battalion completely off is not something that could be overcome by other means.
As it is I consider the 4 Panzerartilleriebataillons; 2 Raketenartilleriebataillons and the 3 Artilleriebataillons the minimum. Not to mention that we don't have offensive air assets or plans for them.