Starting in the largest-available scale (AFAIK), as already mentioned there is the (new) Revell 1:72 scale Gato:
This kit depicts a mid- to late-WWII fleet sub fit - with extensively cut-down/AA-armed sail - and is in no sense a "bare foundation", but a beautifully detailed and apparently highly accurate depiction. Accurate to what specific boat(s) - or whether to Gato herself - and during what specific time period(s), I don't know.
Several aftermarket manufacturers, including White Ensign Models, (I think) L'Arsenal, definitely Nautilus Models and IBS/East Coast Armory quickly jumped on making accessories - mostly alternative/upgraded weapons - however the latter two, Nautilus and IBS began (and apparently will continue) expanding into much more extensive conversions for this kit, and between them their selection of WWII-era sails is already impressive, particularly IBS, which is apparently aiming to cover every USN fleet boat, at any time during WWII - a truly mammoth undertaking. In addition, IBS is also undertaking to offer most, if not eventually all, of the post-WWII "Fleet Snorkel" and "Guppy" conversions - again a very tall order, to cover the entire range, but they have already made quite a good start.
The two primary drawbacks of any of the above options, for the 1:72 fleet boat are: 1) expense - neither the base kit, nor (especially) the conversion sets are what you would call "inexpensive" - and, 2) size. While the latter is actually a great benefit to R/C modellers, at 4 feet or so in length, you've got to have some serious room to store (and to decently view) this model. Size, in turn also feeds back into cost, as everything from paint, to putty, to glue and even mounting materials will add up to significant expense.
Both the above can be reduced by (more than) half, using the next-smaller (plastic) kit - at half the size - namely the Trumpeter 1:144 Gato:
This was the initial boxing - the "As-Built" USS Gato - which was followed by a mid-WWII USS Gato molding, which included "Cut-Down" sail and the (first) modified limber hole pattern applied to Gato herself, though not to the majority of other fleet boats, during the majority of WWII. Both molds appear to be quite accurate to their respective depictions - very much appreciated from Trumpeter, in particular, who have a nasty record of introducing some major innaccuracy or other - usually into the (below-waterline) hull.
Again, when this kit first came out there was the "mad rush" and competition among the "usual suspects" - the aftermarket manufacturers, above - to provide alternate/improved deck- and AA guns for it. And again, IBS and Nautilus Models embarked on far larger product lines, including much more extensive conversions, in whose releases - including again the distinctive post-WWII conversions - IBS is currently ahead, but at the same time, Nautilus' offerings are predominantly of different WWII subjects than chosen by IBS, with significantly more, including several postwar fits, promised for future release by Nautilus.
Just slightly smaller - but with disproportionately large savings, on not just accessories but particularly the kit itself, which is an old classic of widespread circulation, still in production to boot - is the Revell 1:178 scale Lionfish:
This kit being so old, there are first of all some innaccuracies in the mold, including the limber hole- and weld-line patterns - not correct for any fleet boat, ever, AFAIK - and some modellers have also pointed out slight inaccuracies in some hull dimensions. However the former are only in raised-releif outlines - very easily sanded off, in correction - and the latter, whatever their true extent, do not detract from a very convincing appearance of the hull for a fleet boat.
Again, due to the age of this mold, accessory lines are also pretty old - such that some have become very extensive, while others, originally also very large in selection, are by now seeing (at least) several discontinuations. IBS provides an example of the former, with their original, penultimate line of post-WWII conversions - including even a whole Guppy (streamlined) bow replacement - with yet more apparently coming under development still. Nautilus Models also had a substantial line of upgrades, of which many - predominantly for WWII fits, but also including (at least) one postwar "Fleet Snorkel/Guppy" sail - are still offered, though several others have now been discontinued. Still - again, due to the age/distribution involved - many of these can be found on eBay and/or model shows, if you can do some searching for them.
Finally, for a very manageably small project - in size, complexity and particularly in expense (which is definitely where I come in ) - modellers can consider the Lindberg 1:250 scale "Gato":
"Gato" in quotes, above, because - typical of many (especially older) Lindberg kits - the mold contains features of other disparate fits/classes: a small, Cut-Down type of sail much more typical of the Balao class in WWII, as well as raised deck planking - which didn't appear until post-WWII. Still, sail itself - while lacking in detail, along with the rest of the mold - has the correct overall dimensions, as does the hull (though the latter has a strangely upward-flaring contour, aft. As such, the kit does provide a suitable foundation for improvement/conversion - particularly at the price of as little as $3 or so, in the toylike boxing, above. Undoubtedly due to the latter, no aftermarket accessories (AFAIK) have ever been released for this kit, by anyone. However, low cost is precisely what could enable extensive correction/conversion, at reasonable total expense.
The original, 50-plus-year-old molding of this kit - IIRC first released by "O-Line" - did, I believe have an As-Built Gato sail (of unknown fidelity). However such an antique, if still in any kind of decent shape, would today be a collectors item worth far more untouched, than the cost of most if not all the above options. A built, "boneyard" example, however, might again be obtainable (at very low price) on eBay, etc..
In any case, this mold could serve as foundation for an upgrade/conversion both large enough to display significant detail, while small enough for very convenient accommodation, and exhibit.