Expansion Tank - Where to squeeze it?

I have a 2400 sq. ft. living space across 2-floors heating via a Munchkin 80M w/Vision 1 ODR. My PRV started leaking. I replaced it. It's still leaking. Checked system pressure and it was 30-32 psi. Checked expansion tank, thud - dead. Went to replace with a EX-30 based on my boiler's Net BTU as per Extrol's calculator and realized my system has a EX-15 and there is no physical way to jam the EX-30 in there. I feel fairly certain the EX-15 is undersize for my system. I'm wondering whether or any of you think it would be mildly kosher to remove the EX-15 and re-route it's line up towards the alcove ceiling where I could mount an EX-30 off a Nexus Flexconsole via some PEX and maybe push-on connectors? I can solder pipe, but if push-on is satisfactory then I'll go for that since it'll go in faster. I also realize that the lifespan of this boiler is nearer to the end since some critical parts aren't available anymore. I service this boiler and replaced the blower fan assembly myself several months ago after troubleshooting an intermittent failure of the original. This is a R1 80M from 2006. I also installed and programmed the Vision 1 ODR. The boiler is controlled by a t-stat since I have a very leaky house and tried dialing in the curve to run 24-7, but due to improperly sized baseboard and drafts, living spaces would invariably become too hot or too cold. There was no temperature consistency through the house. Main turn on via the t-stat with the Vision 1 handling water temp control while running has been the best I can do. Utility costs are affordable so that's not a driving factor to get this system perfect. So, surely this whole mess will get replaced within the next few years. But, I want to try to keep it going as long as it holds together before an irreplaceable part fails. Thanks folks for any advice! ...and speaking of expansion tanks, my hot water heater doesn't have one. Should it?