As far as I understand the procedure, Tixati keeps all working files in the memory.
Only the abandoned pieces are written and safed on HD.
Problem is, when you have a seeder with 1 KB/s and the piece is 8 MB,
you have to wait about 4 to 5 hours until its done.
What happens, when you have a Blackout oder computer crash after 4 hours?
Its all gone.
I think, your competitors write the piece in progress to HD after 2 Minutes,
and every 2 Minutes after that, no matter how much is actually done.
That really safes a lot of time and worry, if our "perfect" computer systems
show us the ugly side of crashing.

Seems like Tixati concentrates too much on the high speed DL's.
But the real problems are the very low speed DL's.

No offense, but if one seeds with only 1kb/s something is wrong.
This numbers fit more to the e-donkey network (just kiddn).
But yea, worst thing what could happen is that you have to download a chunk again, after resume.
Have you checked other clients, how they handle the caching? Imho this is a standard procedure and the loss of a chuck can happen on any client.

I have used uT before and they handle this matter very nice.
uT writes the parts of the pieces on HD after ( I think) 2 minutes.
Unfortunately uT became so loaded with ads and featured DL's,
for me its a No-Go to use uT again.

But Tixati focuses too much on high speed DL.
But for me, it does not matter at all,
if a DL has 300 KB/s or 320 KB/s.

The problems are the really low speed DL's,
where 10 peers are waiting for 1 seeder
and it takes 2 weeks for the last 5 % of the file.
I had that case already a few times.

Here, in this case, you should really take a good look at your competitors.

Frequent writes to hard drive have an obvious disadvantage: more disk usage. HDD is already heavily used by bittorrent program. I guess, as an option it would be OK.

We talk about a block of a piece, that is like 16 KB or maybe a few more blocks like 256 KB.
And if Tixati saves that for example every 5 minutes, I can't see the extra load on a HDD,
where you can transfer Gigabytes in a minute.
At least as an option I would definitely vote for.

Usually Tixati downloads more than one piece at a time. Also small pieces aren't affected that much, they are written often enough already. Problem is with large pieces, because Tixati writes them less often and potentially you can lose more data. I think a few half complete 8MB pieces, written every 2 minutes, will add some work for HDD, even more if a couple of torrents are downloaded simultaneously. This mechanism won't help much in case of system crash or power outage, if pieces are written too seldom. However when they are written often, HDD will have more work, not needed in normal conditions. I'm not against this idea, but personally I would rather lose some data from time to time.