Assuming you have no size in mind, I'd agree with the 300 size. I don't know the advantages/disadvantages of titanium vs. aluminum, but I'd imagine a titanium sideplated/framed reel would be a bit pricey. Keep in mind, Shimano will be coming out with the Calcutta 300TE very soon, which will be THE 300 sized reel, but at $350 bucks, it's quite a price to pay. So, if you want to try to beat the 300TE, it will have a very high price tag, plus you won't have the name recognition that Shimano has, or the already established customer service. So, saying that you want to make THE reel, may be pushing it. With that said, you could make a really sweet reel that's affordable for guys like us!!!

Here's a quick tip- the bigger the drags the better. All the progear reels have drags equivalent to the next size up in the Penn line, ie the 500 sized progears have 4/0 drags. The 4/0 sized progears have 6/0 drags, etc. (that's part of the reason they're so popular) A 300 size reel with like 500 size drags would be awesome. Of course you'll have to increase the size of the gear box, and probably the main gear which would consequently increase the gear ratio, but something could be worked out, I'm sure. Maybe messing around with the threading of the main and/or pinion gears, or engineering some type of drag stack system that doesn't directly sit on top of the main gear, and is thereby not limited to the size of the main gear.

This is a great topic, BTW, and thanks for bringing it here!!! I could go on and on about this, and I'm sure I will... LMAO.

IMO, if it's over $300 for a 300 sized reel, there will be very little market for it. I don't know why Shimano made a $350 300 sized reel before they made a $175 priced one. So, like I said, don't go for the best, most expensive reel, go for what there's a market for. Right now, there are no reel top quality 300 sized reel available with all the basic features necessary.

I agree with Rob on the handle assessment. Maybe an upgrade handle like the calcutta 400 has would be necessary, because a power handle might overpower a reel of that size, while a standard bass handle might be right for it, but that's something that you can only tell by testing on the water. I also think that some type of padded handle would be nice. Something with hypalon might be taken as ripping off progear, so I'd go with a handle with molded plastic and some type of grip material over it (like the newer penn handles).

Level wind is a tough one. Normally I'd say no level wind because I hate them. But, a 300 sized reel might need a level wind. It might also be a pain to wind line back and forth on that small of a reel. If you do include a level wind, make it non tracking like Shimano's, not tracking like Penn's. The tracking level winds that track back and forth while the reel's in free spool can hamper casting.

A very important, but seemingly overlooked feature is a rod clamp. Make sure to include a rod clamp, or have on available to fit the reel. I know lots and lots and lots of guys will be fishing these reels for calico bass (the 300 size is the ideal calico bass size) and at least half of em will want it on a cork taped rod with no reel seat (myself included).

I'd look into the possiblitly of a magnetic casting control, like on the Daiwas. There may be corrosion problems with this, but I'm really not sure. You might want to look into that.

A clutch bar is a MUST. Penn has a reel (955) that is almost the right size, but since it has the push button instead of the clutch bar lots of guys don't like em.

As for bearings, get the best you can afford for the reel. The more bearings the better, but you don't need as many as a calcutta TE. You don't need 4 bearings in the handle and 8 on the spool shaft and 4 on the gear shaft, etc. But you want more than a Corsair...

For drag material, go HT100. There's no substitute. This is considered the best drag material by long rangers, inshore fishermen, everybody. Dartanium is good, but it hasn't really been put to the test, and it hasn't been around long enough. HT100 is tried and true, and it will attract a lot of attention if it has HT100's right out of the box. It's freakin made from airplane brake material for god's sake... ;-)

If I could combine the best features of all the reel companies it would be as follows:

Shimano- smoothness, customer service, castability.
Penn- strength, availablity/interchangeablity of parts.
Daiwa- magnetic casting control.
Progear- strength, drag systems, handles, freespool.
Newell- weight, spool weight, castability.

Definitely star drag. There's no reason to consider lever drag. It will only hamper freespool. You don't need 20 pounds of drag on a small reel like that.

An interesting thing to mess around with would be the anti-reverse. Every company seems to have their methods. The one weakness of the Calcuttas is the roller bearing. It corrodes quite easily. Maybe a modified roller bearing would work, but I think if you're going to try to stick big drags in there you'll probably need to go with a standard dog. It won't be as smooth but it will be a hard core saltwater whoopin @$$ reel. That's kind of a toss up. You can go for sure strenght with the dog, but sacrifice smoothness, or you can try to engineer something that's smoother and hope it doesn't pop when you've got the drag buttoned on a bluefin with the big drags. That may be your toughest part in the design.

Make sure the spool is light. Go graphite if you have to, but make sure it's light.

Try to avoid using dissimilar metals in direct contact with eachother. This is a corrosion problem waiting to happen. Even the Progears have this weakness. There's a few things people frown upon when they open up a new reel. One is dissimilar metals in direct contact with eachother. Two is plastic parts in important places (corsair...). And of course there are many others, but I won't list them all for you... and this brings me to my next point-

NO PLASTIC INSIDE THE SIDEPLATES. Just open up a Penn reel and look at what's metal and what's not. The only exception would be some type of apparatus for the casting control, or other low-stress part. But things like the eccentric, dog, yoke, bridge etc. can not be plastic. It is absolutely essential that all of the standard, load bearing parts which are necessary for the reel to perform basic functions over and over and over be metal. After enough use and enough abuse, and plastic part will break. Metal will last a while longer.

I guess that's all I can think of at the moment. Great topic, and thanks again for posting. You've got mail.
-Brian