It's not such a complex task to kill Japanese light stuff in the DEI.
Suppose the enemy skips Philippines. He just doesn't conquer them.
You send Catalina in the theater leaving relatively few in the Pacific. That's a very big tradeoff but that has also been my choice.
PH => Midway => Guam => DEI. Both Catalina and B-17.
Now, you have very few locations able to support torps. Namely, Manila-Soerabaja-Singers.
If the enemy has skipped Philippines invasion and has done a huge Mersing gambit at 7-DEC, he will have for sure a lot of stuff to be moved around Philippines going to the DEI. That's where you can hurt him. Either he assigns LRCAP (not working well and short-legged) or he uses a random CVL with fighters as an escort for his convoys. But he has many many relatively little TFs moving around.
Your guys make few hits and sink a lot of stuff combined with aggressive SS and NavS.
I also employ extensively (well... "extensively" relative to the numbers present in the area at the start...) both Seagulls and P-40 in LowN. They are doing really well. I just obliterated a little TF with xAKs/xAKLs/PBs near Davao using those P-40s in LowN.
I think it's better to use those P-40s in this way, while I wait to buy them out of the area, rather than make them cannon fodder for Formosa's Zeros.
When the enemy approaches Java, also, it can be interesting to use Catalina in NavT. Of course, any competent Japanese player will bomb your AFs into oblivion and attack with strong aerial cover from CVLs and/or CVs, but... There is always something which goes wrong, some mistakes, some random reacting in the general mess of TFs going around, pesky allied PTs engaging over and over and... At that point you try to sneak in your stuff into an open AF (I generally use Madioen; AF=4, not on the sea and on good terrain) and unleash your guys over enemy's scattered TFs. Those which eventually go on enemy's AirTFs will be murdered, the others will do some damage.
It depends on your grand strategy. I personally like to have huge allied losses in the DEI buying few days to prepare Burma if I opt for a Burma defence. Few days can mean a couple of Australian DIVs more into the theater. Not much, not little.
Also from Singers: once the enemy has attacked Mersing, he generally retreats his TFs. It means that you can punish his attempts of attacking other positions pretty well given the naval attack mechanics of the game. For example: a classic move is to rush on Mersing, unload a huge amount of stuff, retreat and then attack N-E Borneo. You can kill several stuff during the move over N-E Borneo: your TBs haven't the range to threat them during the approach, your Catalina do.
Enemy's LRCAPs aren't a big problem. Enemy's CAPs are, but in case I soften them using B-17s I deployed from Philippines and PH. They damage all those pesky A6M2s/Oscar-Ics and then I am pretty sure Catalina can do their honest job.
It's just a matter of playing with ranges, positioning, NavS/SigInt, psychology and numbers. I do not say you kill the KB with a random group of Catalina, but I highlight that you can capitalize pretty well many opportunities and that's all I look for: side attacks on the enemy, capitalization over his mistakes, random hits/kills to slow his operations down.
For me, it's a matter of strategy. My grand strategy requires more time than what I do have with Mersing at day-1 and Philippines skipped, therefore I do what I can to gain every little bit of time to arrive at Jan-42 when my Burma defences will be ready and Indian Theater strongly reinforced.
In the meanwhile, I am perfectly open to lose the whole Pacific region to Japanese. Including PH if needed. I play DEI with the obvious idea of losing badly the ballte but accomplishing a strategic gain where it is important to me. That's why I throw into the meatgrinder extremely relevant assets such as Catalinas or B-17s.
I even sent a random Australian DIV to set up a tougher fight in Java. I know they'll die miserably. They'll buy some time, though.