ATTiny85 - Using arduino bootloader with rs232 connection - Sanity check

Hi, this is my very first post here on arduino forums. Im still beginner in everything and this post is really an sanity check for a project thats still running in early stages.

General idea is that i want to make a board that has both ATTiny85 as MCU and ST microelectronics L6470 stepper driver on same board. Furthermore i want to communicate with the ATTiny with a RS232.

So from what I understand I need a programmer to program the ATTiny85 to have arduino bootloader. For this I've found that sparkfun has made a easy to use usb based programmer.

Next I need to use Maxim max3323E chip to convert the rs232 to ttl in order to communicate with the mcu. I've found a tutorial about that here. From what I understand that it is possible to code the MCU like that without using any USB.

I only need the SPI communications for the stepper driver really and I've already made somewhat working code with arduino uno. I just want it to be more compact and standalone board to control the stepper motor with rs232.

Does anyone notice anything that i might have missed?

Usually you don't use a bootloader with the Tiny85, the IDE might say "burn bootloader" but in this case that means "set the fuses."