Much of what I know about these units is what I have learned from you.
As to my "conclusions," I have reviewed the CSR's for soldiers of the various regiments represented in these three consolidated units and the Official Records. From these sources, I have bracketed the known dates as follows:
First-A few references to the "field consolidations" that you mentioned:
11/12/63 Lt Pittman unconditional resignation-HQ 19th & 15th &… [?] th....appd LtCol H G P Williams cdg regt
12/8/63 near Washington, Ark-HQs 20th & 12th Ark reg’ts & 12th Bn Ark vols-resignation of Capt Glascow of 12th Ark-appd Col Jones 20th Ark-endorsed/appd-HQ P & E prisoners Washington, Ark-Gen Dockery cdg
Second-It seems from the following references that the regiments resumed their separate identities by time of the April campaign against Steele in Arkansas:
4/20/64 Dist of Ark-Price
Fagan's cavalry division
Dockery's Bgde
18th Ark
19th Ark-Williams
20th Ark
12th Ark Bn SS
4/30 Jenkins Ferry battle-
H G. P. Williams-Lieut. Col. Cdg Infy [Portion] Dockery's Brig-"I carried into action nearly 400 men, divided into 4 small dtchmts, under Captains Drewry & Etris, Major Southerland, & Lt Gillespie, composing the Infantry portion of Gen Dockery's Bgde.
The dismtd casuals of Dockery's Bgde had been formed in to a Regt of 4 Co’s under Lt col. H. G. P. Williams’ command attached to Churchill's Div
15th Ark Inf, under Capt. Austin K. Etris
18th Ark Inf, under Maj. Samuel H. Southerland
19th Ark Inf, under Capt. Thomas M. Drewery
12th Ark Bn, under First Lieut. James A. Gillespie
Third-Earliest known references to the 1st-2nd-3rd Consolidated Regiments appear as:
7/22/64 HQ 1st Consol regt W W Reynolds LtCol cdg-Dockery’s bgde near Monticello-Lt Scott 14th Ark [Powers] now part of 1st Ark consolidated- to be dropped-absent without leave since 2/1/64-appd Dockery & Fagan
9/22/64 K Smith to Gen Greer cdg conscripts-The Gen cdg directs that you will order out the Reserve Corps of the State of Ark. You will instruct -Gen Dockery that as soon as ready for field service he will report to the district commander for instructions.
9/23 Monticello-Spec orders Churchill’s Division
I. Gen McNair having been assigned to the command of the brigade of Ark infantry known as Dockery’s brigade, and having reported to these hqs, will immediately enter upon the discharge of the duties as cdr of said brigade.
II. Gen'ls McNair & Hawthorn will transmit to this office as soon as possible a complete register of the commissioned officers of their entire commands, giving names, rank, age, date of appointment, of election, by whom appointed, State appointed from, native State, and number of regiments as reorganized by the War Dept
Sept 64 returns
Gen McNair
1st Ark consol-Lt Col W. W. Reynolds
2nd Ark consol-Col T.J. Reid
3rd Ark consol-Col H. G. P. Williams
From the sources mentioned, I have concluded that the late 1863 "field consolidations" of the various regiments [such as-HQs 20th & 12th Ark reg’ts & 12th Bn Ark Vols] were being used during the parole and exchange period following the Vicksburg and Port Hudson surrenders.
By the time of the Spring 1864 campaign, we see them identified as individual regiments [under their original numeric designations] with some serving mounted under Dockery in Fagan's cavalry division and others dismounted and attached to Churchill's infantry division.
The July 22, 1864 reference to the "1st Arkansas Consolidated" is the first I have seen in these sources that uses the "Consolidated" designation.
In September, Dockery is transferred to the reserve corps, and McNair assumes command the units identified in the September 1864 returns as 1st-2nd-3rd Arkansas consolidated.
The conclusion being that sometime after the spring 1864 campaign and before July 22, 1864, the regiments assumed their "consolidated" identities.
Finally, I believe Hardy's regiment [19th/24th Ark] was actually in Tappan's brigade and not part of the 3rd Arkansas Consolidated. I believe it was Dockery's 19th Arkansas instead that was in McNair's brigade as part of the 3rd Arkansas Consolidated.