Warships proved surprisingly robust in operations against aircraft. That being said, warships could not stand long under hostile skies without taking attrition. The question is at what range the battle is fought from the German air bases, the number of sorties the LW is able to generate against warships, the types of sorties, (dive, level or low level bombing, or strafing), the ammunition state and formation of the warships being attack, (AA formation and lets go blow up barge formations being quite different), and quite importantly, the ability of the RAF to break up attacks on warships.
Glenn, considering you have participated in the latest stem-winder on this subject at AHF since 23 November 2019, I'm surprised you are unable to post some of the information presented. Such as a typical Stuka in the first five days of GELB, arguably the peak of the arm in 1940, managed an average of 3.17 sorties per day, but over the entire period 10 May-8 August averaged 1.68 sorties per day.
Oh, and trying to paper over yet again the complete inability of the Luftwaffe to attack the Royal Navy at night is a nice touch.
In order against warships, the LW aircraft were probably the Stuka, then the ME-110 (ground attack), ME-109 (fighter bomber), JU-88, (level or dive bomber), HE-111/DO-17 (level bomber). The number of Stukas available for Sealion would probably not have exceeded about 300 and they would be overtasked between sea and land support roles.
The Bf 110 (not "ME") was not a ground attack aircraft at this time. It was a a heavy fighter intended for bomber escort and air superiority missions. The Bf 109 was not a fighter bomber, it was an interceptor pressed into bomber escort and air superiority missions dues to the failure of the interwar development of the heavy fighter doctrine. The only two units of Bf 109 and Bf 110 that existed as of mid to late September 1940 with a ground attack - not maritime attack, which was as different a kettle of fish in practice as was the difference between "AA formation and lets go blow up barge formations" were Erprobungsgruppe 210 at Denain and II. (Sch.)/LG 2., which transitioned from Hs 123 to Bf 109E-4/B at Braunschweig-Waggum between the end of ROT and its deployment to Calais-Marck on 6 September 1940. As of 7 September, Erpr.Gr.210, which had been very successful in airbase attacks in August, albeit at heavy loss, was down to 26 aircraft, 17 of which were operational (probably one-third were Bf 109). II. (Sch.)/LG 2 had 33 aircraft with 27 operational.
We also had the long discussion regarding the state of the Stuka forces and you have yet to come up with a good explanation for how four of eleven operational groups with a total strength of 123 operational aircraft suddenly "would probably not have exceeded about 300" given one Gruppe, III./StG 2. was at Kitzingen rebuilding until December 1940 when it deployed to Trapani as part of the German reinforcement of the Italians in the central Mediterranean and an entire Geschwader, StG 77. appears to have been non-operational following the loss of 21 aircraft and crews out of 87 committed on 18 August. From then on it appears to have been rebuilding and training, the latter with harrowing results since it lost four aircraft and four crewmen, including two pilots, in a training accident on 11 September, and another midair on 19 October that cost two aircraft and crew. Part of the problem may have been the reorganization of StG 77. in mid-July. In its I. Gruppe, 3. Staffel was transferred to become 2./Erpr.Gr.210 and transitioned to Bf 110D-0 (which must have been interesting), while III. Gruppe was formed II./KG 76, which had been in the middle of transitioning from Do 17Z to Ju 88A (which must have been even more interesting). It seems the Geschwader lost most of its mojo and did not regain it till the spring of 1941.
Oh, and yeah, the Stuka would have been "overtasked", just like the rest of Luftflotte 2. and 3.
The RAF would not be too effective against small ships in the Channel. Probably a threat mostly to the larger steamers and the invasion beaches themselves, but I still doubt they'd hit much. The fighters would be too busy elsewhere and were under armed anyways. The Royal Navy though, was a different story. But Sealion did have a large number of aux. warships such as Siebel ferries and minesweepers that would have absorb a lot of attention.
"Siebel ferries" were never "aux. warships" and there was considerable controversy between the KM, LW, and H over exactly what its role was in the event of an attack. The KM was terrified, possibly justly, that the inexperienced crews of the various "aux. warships" would let fly at whoever spooked them and wanted them to hold fire until reaching the assault area. The Heer wanted them to be able to fire at whatever and whenever, so long as doing so protected their troops. The Luftwaffe wanted them to fire on British aircraft because, well that was what they were supposed to do. Aside from that the "aux. warships" consisted of 27 leichte and 5 schwere Artillerieträger, mostly large trawlers, fitted with one 15cm SK/C and two 2cm Flak in the schwere, except for one with two 10.5cm SK/C as main armament, or one 7.5cm (a captured French or Belgian "French 75") and a 3.7cm in the leichte, none of which were intended for anything other than support of the landings. The numerous V-Boot were small trawlers usually fitted with a single 3.7cm or 2cm gun.
Otherwise, except for the 20 S-Boot, the 5 Z-Boot, and the 5 T-Boot, the only regular "warships" were the big M1935 M-Boot with its two 10.5cm guns...all 17 of them, and the R-Boot with its single 2cm gun.
Note that virtually all the R-Boot and V-Boot were also required to do double-duty carrying elements of the Vorausabteilungen to the beaches, so were crowded with 20 to 60 infantrymen getting in the way and vomiting during the passage.
Anyway, this latest round of what if silliness induced me to reread Schenk after almost 20 years, which has confirmed just how shambolic, confused, and riddled with wishful thinking the German planning was. I had forgotten for example the silliness of how they three services were tasked to do plans in July, did so independently for about six weeks, and THEN got together to compare notes. Surprise! They all came up with completely different and incompatible plans (well, the KM and Heer did, the LW tried to pretend they didn't need no stinkin' plans). Or how it was planned it would take 14 hours to unload one of the big "steamer" transports, because a unit practiced doing so in a protected harbor, with four barges alongside at all times. And so on...